U.S. patent application number 14/536171 was filed with the patent office on 2015-02-26 for highly scratch-resistant coatings having good weathering and crack resistance.
The applicant listed for this patent is BASF Coatings GmBH. Invention is credited to Manfred Essig, Michael Kutschera, Andreas Poppe, Egon Wegner.
Application Number | 20150056458 14/536171 |
Document ID | / |
Family ID | 39271697 |
Filed Date | 2015-02-26 |
United States Patent
Application |
20150056458 |
Kind Code |
A1 |
Poppe; Andreas ; et
al. |
February 26, 2015 |
HIGHLY SCRATCH-RESISTANT COATINGS HAVING GOOD WEATHERING AND CRACK
RESISTANCE
Abstract
Disclosed is an at least partly crosslinked coating (K) composed
of a near-surface coating zone (K1) and a volume coating zone (K2),
the coating obtained from a composition comprising at least two
different crosslinkable components (D1) and (D2), at least part of
component (D) having one or more surface-active structural units,
wherein (i) the coating in zone (K1) and in zone (K2) is at least
partly crosslinked, and (ii) the crosslinking density of the
coating in zone (K1) is higher than the crosslinking density of the
coating in zone (K2). Also disclosed are coatings (K) wherein the
concentration of component (D1) in the near-surface coating zone
(K1) is higher than in the volume coating zone (K2), and the
micropentration hardness and/or the dry scratch resistance of the
coating (K) is higher than that of an at least partly crosslinked
coating (K') obtained from a composition with no crosslinkable
component (D1).
Inventors: |
Poppe; Andreas;
(Sendenhorst, DE) ; Wegner; Egon; (Greven, DE)
; Kutschera; Michael; (Limburgerhof, DE) ; Essig;
Manfred; (Otterberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BASF Coatings GmBH |
Munster |
|
DE |
|
|
Family ID: |
39271697 |
Appl. No.: |
14/536171 |
Filed: |
November 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12531347 |
Feb 17, 2010 |
|
|
|
PCT/EP2008/000487 |
Jan 23, 2008 |
|
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14536171 |
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Current U.S.
Class: |
428/447 ;
427/387; 524/506 |
Current CPC
Class: |
Y10T 428/24992 20150115;
Y10T 428/31663 20150401; C08L 75/04 20130101; C08L 33/04 20130101;
C08L 61/28 20130101; C09D 7/48 20180101; C09D 161/28 20130101; B05D
7/532 20130101; C08J 3/245 20130101; C09D 133/08 20130101; B05D
7/577 20130101; C09D 133/04 20130101; Y10T 428/2495 20150115; Y10T
428/24983 20150115; C09D 133/04 20130101; C08L 2666/20 20130101;
C09D 133/04 20130101; C08L 2666/16 20130101; C09D 161/28 20130101;
C08L 2666/04 20130101 |
Class at
Publication: |
428/447 ;
524/506; 427/387 |
International
Class: |
C09D 133/08 20060101
C09D133/08; B05D 7/00 20060101 B05D007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2007 |
DE |
102007013242.7 |
Claims
1. An at least partly crosslinked coating (K) comprising 1. a
near-surface coating zone (K1) and 2. a volume coating zone (K2),
the coating (K) being obtained from a coating composition (B)
comprising at least two different crosslinkable components (D1) and
(D2), at least part of component (D1) comprising one or more
surface-active structural units (O); wherein (i) the coating both
in zone (K1) and in zone (K2) is at least partly crosslinked, and
(ii) the crosslinking density of the coating in zone (K1) is higher
than the crosslinking density of the coating in zone (K2).
2. The coating of claim 1, wherein the at least partly crosslinked
coating (K) exhibits a chemical disuniformity in the form of a
gradient perpendicular to the surface (KO).
3. The coating of claim 2, wherein the at least partly crosslinked
coating (K) exhibits a chemical disuniformity in the form of a
gradient of silicon atoms of type (Si 1) and/or of type (Si 2)
##STR00005## perpendicular to the surface (KO), where
R.sup.S1=organic radical, preferably linear and/or branched
alkylene or cycloalkylene radical having 1 to 20 carbon atoms,
R''=alkyl, cycloalkyl, aryl or aralkyl, the carbon chain possibly
being interrupted by nonadjacent oxygen, sulfur or NRa groups, with
Ra=alkyl, cycloalkyl, aryl or aralkyl.
4. The coating of claim 2, wherein the gradient in the chemical
disuniformity leads to a gradient in the physical properties
perpendicular to the surface.
5. The coating of claim 2, wherein the gradient has a half-value
depth <1 .mu.m.
6. An at least partly crosslinked coating (K) comprising 1. a
near-surface coating zone (K1) and 2. a volume coating zone (K2),
wherein (I) the coating (K) is obtained from a coating composition
(B) comprising at least two different crosslinkable components (D1)
and (D2), at least part of component (D1) having one or more
surface-active structural units (O), and (II) the concentration of
component (D1) in the near-surface coating zone (K1) being higher
than in the volume coating zone (K2), wherein the micropenetration
hardness and/or the dry scratch resistance of the at least partly
crosslinked coating (K) is higher than the micropenetration
hardness and/or the dry scratch resistance of an at least partly
crosslinked coating (K) obtainable from a coating composition (B')
which contains no crosslinkable component (D1).
7. The coating of claim 1, wherein the film thickness of the
near-surface coating zone (K1) is between 1 nm and 500 nm, and/or
the ratio of the dry film thickness of the near-surface coating
zone (K1) to the dry film thickness of the volume coating zone (K2)
is less than 0.1.
8. The coating of claim 1, wherein the crosslinkable component (D1)
has silane groups as crosslinkable groups.
9. The coating of claim 1, wherein the surface-active structural
elements (O) comprise at least one member selected from the group
consisting of hydrocarbon radicals and their derivatives,
fluorinated hydrocarbon radicals, fatty acid radicals, the radicals
of fatty acid derivatives, unsubstituted siloxane radicals, and
substituted siloxane radicals.
10. The coating of claim 1, wherein the crosslinkable component
(D1) has been prepared by modifying at least part of a precursor of
component (D1) and/or at least part of component (D1) with one or
more surface-active compounds (OV).
11. The coating of claim 10, wherein (i) the surface-active
compound (OV) comprises at least one member selected from the group
consisting of hydroxyl, epoxy, isocyanate, carbamate, carboxyl,
anhydride, amine, thiol, ethylenically unsaturated double bond, and
combinations thereof, and/or (ii) the crosslinkable component (D1)
and/or a precursor of the crosslinkable component (D1) comprises at
least one complementary functional group selected from the group
consisting of hydroxyl, epoxy, isocyanate, carbamate, carboxyl,
anhydride, amine, thiol, ethylenically unsaturated double bonds,
and combinations thereof.
12. The coating of claim 11, wherein the compound (OV) is a
siloxane of the formula (I) ##STR00006## where R.sup.1 to R.sup.6
are identical or different radicals and R.sup.1=alkyl, cycloalkyl,
aryl or aralkyl radical, the carbon chain possibly being
interrupted by nonadjacent oxygen, sulfur or NRa groups, or
fluorine-substituted alkyl, cycloalkyl, aryl or aralkyl radicals,
R.sup.2=hydroxyl, alkyl, cycloalkyl, aryl or aralkyl radical, the
carbon chain possibly being interrupted by nonadjacent oxygen,
sulfur or NRa groups, R.sup.3 and R.sup.6=hydrogen, alkyl,
cycloalkyl, aryl or aralkyl radical, the carbon chain possibly
being interrupted by nonadjacent oxygen, sulfur or NRa groups, or
fluorine-substituted alkyl, cycloalkyl, aryl or aralkyl radicals,
R.sup.4 and R.sup.5=hydrogen, hydroxyl, alkyl, cycloalkyl, aryl or
aralkyl radical, the carbon chain possibly being interrupted by
nonadjacent oxygen, sulfur or NRa groups, at least one of the
radicals R.sup.2, R.sup.4, and R.sup.5 additionally carrying a
functional group which is reactive toward the complementary
functional groups of component (D1), and m.sub.1=1 to 80, and
m.sub.2=0 to 80.
13. The coating of claim 11, wherein the compound (OV) is a
siloxane of the formula (III) ##STR00007## where R.sup.1=alkyl,
cycloalkyl, aryl or aralkyl radical, the carbon chain possibly
being interrupted by nonadjacent oxygen, sulfur or NRa groups, or
fluorine-substituted alkyl, cycloalkyl, aryl or aralkyl radicals,
and R.sup.4=hydrogen, hydroxyl, alkyl, cycloalkyl, aryl or aralkyl
radical, the carbon chain possibly being interrupted by nonadjacent
oxygen, sulfur or NRa groups, and m=1 to 80.
14. The coating of claim 1, wherein the crosslinkable component
(D1) comprises at least one reactive radical of the formula (VI)
--NR'''--C(O)--N-(L-SiR''x(OR')3-x)n(L'-SiR''y(OR')3-y)m (VI) where
R'''=hydrogen, alkyl, cycloalkyl, aryl or aralkyl, the carbon chain
possibly being interrupted by nonadjacent oxygen, sulfur or NRa
groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, R'=hydrogen,
alkyl or cycloalkyl, the carbon chain possibly being interrupted by
nonadjacent oxygen, sulfur or NRa groups, L, L'=linear and/or
branched alkylene or cycloalkylene radical having 1 to 20 carbon
atoms, R''=alkyl, cycloalkyl, aryl or aralkyl, the carbon chain
possibly being interrupted by nonadjacent oxygen, sulfur or NRa
groups, n=0 to 2, m=0 to 2, m+n=2, and x, y=0 to 2.
15. The coating of claim 1, wherein the coating composition (B)
contains component (D1) in an amount of 0.1 to 35% by weight,
and/or the catalyst (C) in an amount of 0.1 to 15% by weight,
and/or component (D2) in an amount of 50 to 99.8% by weight, based
in each case on the nonvolatiles of the coating composition
(B).
16. The coating of claim 1, wherein the crosslinkable component
(D2) is composed of one or more binders (BM).
17. The coating of claim 16, wherein the binders (BM) are selected
from the group consisting of oligomeric and/or polymeric compounds
which have acrylate groups, methacrylate groups, hydroxyl groups,
carbamate groups, epoxy groups, isocyanate groups, and carboxyl
groups, preferably hydroxyl groups and/or carbamate groups.
18. A multicoat effect and/or color paint system comprising at
least one pigmented coating and, disposed thereon, a transparent
coating, wherein the transparent coating is the coating of claim
1.
19. A process for producing the multicoat paint system of claim 18,
wherein a substrate is coated with at least one pigmented coating
composition and at least part of the resulting pigmented coating is
coated with at least one transparent coating composition (B) of
claim 1, and curing is carried out.
20. A method of controlling the properties of at least partly
crosslinked coatings (K), wherein the coating (K) is composed of a
near-surface coating zone (K1) and a volume coating zone (K2), and
the coating (K) is produced from a coating composition (B)
comprising at least two different crosslinkable components (D1) and
(D2), at least part of component (D1) comprising one or more
surface-active structural units (O); wherein (i) the crosslinking
density of the network (N1) formed from component (D1) is higher
than the crosslinking density of the network (N2) formed from
component (D2), and (ii) the properties of the coating are
controlled by way of the ratio of the crosslinking density of the
network (N1) formed from component (D1) to the crosslinking density
of the network (N2) formed from component (D2).
21. The method of claim 20, wherein the near-surface coating zone
(K1) is formed substantially by the at least partly crosslinked
component (D1) and the volume coating zone (K2) is formed
substantially by the at least partly crosslinked component
(D2).
22. An at least partly crosslinked coating (K) composed of 1. a
near-surface coating zone (K1) and 2. a volume coating zone (K2),
the coating (K) being obtainable from a coating composition (B)
which comprises at least two different crosslinkable components
(D1) and (D2), at least part of component (D1) having one or more
surface-active structural units (O); wherein (i) the coating both
in zone (K1) and in zone (K2) is at least partly crosslinked, and
(ii) the crosslinking density of the coating in zone (K1) is higher
than the crosslinking density of the coating in zone (K2), and
wherein the crosslinkable component (D1) comprises at least one
adduct (A) with silane functionality which are prepared by an
addition reaction of (a) at least one silane (S1) which has at
least one functional group which is reactive with the complementary
functional groups of the surface active compound (OV), and (b) at
least one surface active compound (OV) which has at least one
complementary functional group and at least one surface active
radical.
23. An at least partly crosslinked coating (K) composed of 1. a
near-surface coating zone (K1) and 2. a volume coating zone (K2),
the coating (K) being obtainable from a coating composition (B)
which comprises at least two different crosslinkable components
(D1) and (D2), at least part of component (D1) having one or more
surface-active structural units (O); wherein (i) the coating both
in zone (K1) and in zone (K2) is at least partly crosslinked, and
(ii) the crosslinking density of the coating in zone (K1) is higher
than the crosslinking density of the coating in zone (K2), and
wherein the coating composition (B) comprises at least one
amine-blocked phosphoric acid ester as a catalyst (C).
24. An at least partly crosslinked coating (K) composed of 1. a
near-surface coating zone (K1) and 2. a volume coating zone (K2),
the coating (K) being obtainable from a coating composition (B)
which comprises at least two different crosslinkable components
(D1) and (D2), at least part of component (D1) having one or more
surface-active structural units (O); wherein (i) the coating both
in zone (K1) and in zone (K2) is at least partly crosslinked, and
(ii) the crosslinking density of the coating in zone (K1) is higher
than the crosslinking density of the coating in zone (K2), and
wherein the at least partially crosslinkinked coating has a
residual gloss after a Crockmeter test (per EN ISO 105-X 12; 9 um
paper grade) of at least 55%.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional application of Ser. No.
12/531,347 filed on 17 Feb. 2010, which is a National Phase
application of Patent Application PCT/EP2008/000487 filed on 23
Jan. 2008, which claims priority to DE102007013242.7, filed 15 Mar.
2007, all of which are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to at least partly crosslinked
coatings which are highly scratch-resistant and at the same time
exhibit good weathering resistance and crack resistance, and also
to a method of controlling the properties of crosslinked
coatings.
BACKGROUND OF THE INVENTION
[0003] WO05/028550 discloses functional polymers which have a
first, surface-active segment and a second, functional segment
which generates the desired properties of the functional polymer.
These functional polymers are blended with nonmodified
thermoplastic bulk polymers, and the resulting blends are used to
produce moldings or similar articles or to produce coatings, in
order to exert targeted control over the properties of the surfaces
of the articles or coatings obtained. The surface-active
modification of individual film-forming constituents of a coating
composition which is crosslinked only after application to give a
coating having targeted surface properties is not, however,
described in WO05/028550.
[0004] Furthermore, the functional polymers described in
WO05/028550 are employed for biological or medical applications,
such as for cosmetics, for the biocidal treatment of gloves,
clothing, medical instruments, and the like, or for the biocidal
finishing of air filters and the like, and also for the production
of diagnostic chips, by bioactive surface treatment of the
chips.
[0005] The descriptions do include descriptions of
alkoxysilane-functional, surface-active moldings and coatings where
the bulk polymers are treated in some cases with polymeric
additives which have alkoxysilane groups. The curing of the
alkoxysilane groups in those cases is by a number of hours of
moisture treatment or by treatment with aqueous acids. This
treatment, which is typical in the field of plastics parts, is
associated with considerable additional cost and inconvenience in
the field of automotive finishing, however, and is therefore
undesirable. Moreover, clearcoat materials that are typically
employed in the field of automotive finishing are generally
incompatible with the aqueous acids required, meaning that it is
not possible to transpose the functional coatings described in
WO05/028550 to the field of automotive finishing.
[0006] Furthermore, the as yet unpublished American patent
application with the Ser. No. 11/227,867, of Sep. 15, 2005,
describes coating compositions which comprise reaction products (I)
of a dimer fatty acid diol with an
isocyanatoalkyltrialkoxysilane.
[0007] A particular feature of the coatings obtained using these
coating compositions is a very high gloss. As the fraction of the
reaction products (I) of a dimer fatty acid diol with an
isocyanatoalkyltrialkoxysilane in the coating compositions goes up,
the hardness and the resistance to solvents, as measured in double
rubs with methyl ethyl ketone, goes down. In the field of
automotive finishing, however, the demand is increasingly for
coatings having an improved hardness and resistance and hence an
improved scratch resistance.
[0008] EP-B-1 295 914, furthermore, discloses coating compositions
featuring an enhanced oil and water repellency effect, these
compositions comprising an alkoxysilyl-functional acrylic resin, an
acrylic resin containing alkoxysilyl groups and secondary
dimethylpolysiloxane chains, a hydroxyl- and epoxy-functional
acrylic resin, and a polyester resin having a high acid number. On
account of the relatively broad molecular weight distribution of
the poly(meth)acrylates with alkoxysilane groups, however, solids
contents of less than 50% by weight only are generally realizable
in the clearcoat materials. At higher proportions, the coating
materials are difficult to process, on account of their high
viscosity. On curing, moreover, unwanted Si--O--C nodes may form in
competition with the desired Si--O--Si nodes, as a result of
transesterification of the --Si(O-alkyl).sub.3 groups with ester
units of the adjacent alkyl (meth)acrylate comonomer units, the
Si--O--C nodes being hydrolytically labile and leading to reduced
chemical resistance on the part of the resulting coating. Since the
heavy-duty OEM clearcoats are to have as a high a weathering
resistance as possible, it is a concern that, as compared with
polyurethane networks, the poly (meth)acrylate networks exhibit a
reduced weathering resistance.
[0009] That patent, however, describes neither a difference in
degree of crosslinking of the coating in the near-surface layer and
in the bulk, nor the control of the properties of the coating by
means of these differences in the degree of crosslinking.
[0010] EP-B-1 204 701 describes coating compositions which as well
as nanoparticles comprise a surface-active substance, whereby an
accumulation of the nanoparticles at the surface comes about in the
coating, leading to improved scratch resistance on the part of the
coatings. The extent of such structures is usually low, similar to
a chain of beads on the surface.
[0011] Owing to the extremely strong interparticulate interactions
and to the usually incomplete stabilization of the particles,
however, there are frequent instances of particle agglomeration and
hence an adverse effect on the leveling and the appearance of the
resulting coatings. Furthermore, extremely effective stabilization
of the particles is necessary in order to ensure a wide processing
window and to avoid possible deposits in the circuit lines. The
last-mentioned publication also fails to describe either a
difference in degree of crosslinking of the coating in near-surface
layer and in the bulk, or the controlling of the properties of the
coating by means of these differences in the degree of
crosslinking.
[0012] Furthermore, DE 10 2004 050 747 A1 and the as yet
unpublished German patent application DE P 10 2005 045228.0-44
disclose coating compositions which comprise adducts with
alkoxysilane functionality. The coating compositions described
therein are cured using suitable catalysts in the presence, if
appropriate, of small amounts of water, to form Si--O--Si networks.
One of the applications of the coating compositions is as
clearcoats in OEM systems. They lead to coatings having very high
scratch resistance, but are frequently in need of further
improvement in terms of weathering stability and in terms of
cracking. A further disadvantage is the high price of the adducts
with alkoxysilane functionality, that are included in decidedly
large quantities in these coating compositions.
[0013] WO01/98393, furthermore, discloses coating compositions
featuring enhanced adhesion to aluminum substrates, and comprising
not only a hydroxyl-containing binder and an isocyanato-containing
crosslinker but also a silane oligomer (B) having at least two
isocyanate groups, as an essential constituent, said oligomer (B)
being the reaction product of an isocyanate-functional compound (A)
with a coupling reagent (X) which contains at least one
alkoxysilane-functional group and at least one group that is
reactive toward isocyanate groups.
[0014] Modifying the silane oligomers (B) with surface-active
components is not described in that publication. Hence, although
the coatings described in WO01/98393 may have zones of increased
degree of crosslinking, the lack of surface modification of at
least one of the film-forming components means that these zones of
increased degree of crosslinking are distributed at random across
the coating as a whole, and the targeted control of the properties
of the coating by means of these differences in degree of
crosslinking is not possible in the case of the coatings it
describes.
[0015] US 2006-0217472 A1, furthermore, discloses that the scratch
resistance of polyurethane-based coatings can be improved by taking
coating compositions which comprise a hydroxyl-containing binder, a
crosslinker containing isocyanate groups, and a metal catalyst for
the OH/NCO reaction and adding to them an amino silane, such as
bis(3-propyl-trimethoxysilyl)amine, or its reaction products with
isocyanates. Modifying the aminosilanes with surface-active
components, however, is not described in US 2006-0217472 A1, any
more than a difference in the degree of crosslinking of the coating
in the near-surface layer and in the bulk.
[0016] WO 01/09260, finally, discloses coating compositions which
comprise polysiloxanes (a) having at least one reactive group,
compounds (b) which have at least one group reactive with the
reactive groups of the polysiloxanes, and, if appropriate,
particles (c), and further constituents. In the curing reaction,
therefore, the polysiloxanes do not form an Si--O--Si network with
the compounds (b).
[0017] This document too fails to describe a difference in degree
of crosslinking of the coating in the near-surface layer and in the
bulk, and the control of the properties of the coating by means of
these differences in degree of crosslinking.
[0018] The problem addressed by the present invention is therefore
that of providing coating compositions which allow the properties
of the resulting coatings to be set in a targeted way.
Advantageously it ought to be possible by means of these coating
compositions to produce coatings which differ at their surface in
at least one property from the properties of the coating in the
underlying volume element (bulk).
[0019] The aim in particular was to provide coating compositions
which lead to coatings having a high micropenetration hardness and
a high scratch resistance, more particularly a high dry scratch
resistance, as it is known, typically determined in the crockmeter
test. At the same time these coatings ought to lead to a highly
weathering-stable network. Furthermore, the coating compositions
ought to meet the requirements typically imposed in the field of
automotive OEM finishing. The coating compositions ought therefore
in particular to exhibit good haze, i.e., no haze, good leveling,
and a very good overall visual appearance. Finally the desired
properties ought to be obtained as inexpensively as possible.
SUMMARY OF THE INVENTION
[0020] This problem is surprisingly solved by an at least partly
crosslinked coating (K) composed of
[0021] 1. a near-surface coating zone (K1) and
[0022] 2. a volume coating zone (K2),
the coating (K) being obtainable from a coating composition (B)
which comprises at least two different crosslinkable components
(D1) and (D2), at least part of component (D1) having one or more
surface-active structural units (O), wherein [0023] (i) the coating
both in zone (K1) and in zone (K2) is at least partly crosslinked,
and [0024] (ii) the crosslinking density of the coating in the
near-surface coating zone (K1) is higher than the crosslinking
density of the coating in the volume coating zone (K2).
[0025] The invention further relates to an at least partly
crosslinked coating (K) composed of
[0026] 1. a near-surface coating zone (K1) and
[0027] 2. a volume coating zone (K2),
wherein [0028] (I) the coating (K) is obtainable from a coating
composition (B) which comprises at least two different
crosslinkable components (D1) and (D2), at least part of component
(D1) having one or more surface-active structural units (O), [0029]
(II) the concentration of component (D1) in the near-surface
coating zone (K1) being higher than in the volume coating zone
(K2), wherein the micropenetration hardness and/or the dry scratch
resistance of the at least partly crosslinked coating (K) is higher
than the micropenetration hardness and/or the dry scratch
resistance of an at least partly crosslinked coating (K'')
obtainable from a coating composition (B') which contains no
crosslinkable component (D1).
[0030] The invention also provides multicoat effect and/or color
paint systems in which the transparent coating is a coating of the
invention, and processes for producing these multicoat paint
systems.
[0031] Lastly the invention also relates to methods of controlling
the properties of at least partly crosslinked coatings, wherein the
coating (K) is composed of a near-surface coating zone (K1) and a
volume coating zone (K2), and the coating (K) is produced from a
coating composition (B) which comprises at least two different
crosslinkable components (D1) and (D2), at least part of component
(D1) having one or more surface-active structural units (O),
wherein [0032] (i) the crosslinking density of the network (N1)
formed from component (D1) is higher than the crosslinking density
of the network (N2) formed from component (D2), and [0033] (ii) the
properties of the coating are controlled by way of the ratio of the
crosslinking density of the network (N1) formed from component (D1)
to the crosslinking density of the network (N2) formed from
component (D2).
[0034] It is surprising and was unforeseeable that the provision of
coating compositions which comprise at least two different
crosslinkable components (D1) and (D2) and in which at least part
of component (D1) has one or more surface-active structural units
(O) makes it possible to control the properties of the resulting
coatings in a targeted way via component (D1) and also via the
ratio of the crosslinking density of the coating in the
near-surface zone (K1) to the crosslinking density of the coating
in the volume coating zone (K2). The near-surface coating zone (K1)
is more particularly formed substantially by the at least partly
crosslinked component (D1), and the volume coating zone (K2) is
formed substantially by the at least partly crosslinked component
(D2). In accordance with the invention, furthermore, the
crosslinking density of the network (N1) formed from component (D1)
is higher than the crosslinking density of the network (N2) formed
from component (D2). As a result it is possible to improve the
scratch resistance, more particularly what is known as the dry
scratch resistance, typically determined in the crockmeter test,
and/or to improve the hardness of the coating, and at the same time
to ensure high weathering resistance and crack resistance.
Furthermore, the resulting coatings exhibit very good overall
visual appearance and no haze. Finally, the coatings meet the
requirements typically imposed on a clearcoat in the field of
automotive OEM finishing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 provides a cross-sectional illustration of the at
least partly crosslinked coating (K).
[0036] FIG. 2 graphically illustrates the Si/C ratios for the
coatings of Example 1 and Comparative Examples C2 and C3.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
at Least Partly Crosslinked Coating (K)
[0037] The at least partly crosslinked coating (K) is composed of a
near-surface coating zone (K1) and a volume coating zone (K2), as
illustrated in FIG. 1. In said FIG. 1 (KO) represents the surface
of the coating (K) that is facing away from the substrate or from
the pigmented layer (P) located below the coating (K).
[0038] The near-surface coating zone (K1) hereinbelow is that part
of the at least partly crosslinked coating (K) that is in general
parallel to the substrate or to the pigmented layer (P) to which
the coating composition (B) is applied, and that forms the
air-facing surface (i.e., the substrate-remote surface) of the
coating.
[0039] The volume coating zone (K2) hereinbelow is that part of the
at least partly crosslinked coating (K) that extends in general
beneath the near-surface coating zone and that in general is
likewise parallel to the substrate or to the pigmented layer
(P).
[0040] The layer thickness of the near-surface coating zone (K1) is
typically between 1 nm and 500 nm, preferably between 10 nm and 200
nm, more preferably between 10 nm and 100 nm, and very preferably
between 10 nm and 50 nm, and/or the ratio of the dry film thickness
of the near-surface coating zone (K1) to the dry film thickness of
the volume coating zone (K2) is less than 0.1, preferably less than
0.01, more preferably less than 0.005.
[0041] It is essential to the invention that the coating (K) is at
least partly crosslinked not only in the near-surface coating zone
(K1) but also in the volume coating zone (K2).
[0042] The phrase "at least partly crosslinked" means, in the text
below, that the crosslinkable components of the coating composition
(B) are in at least partly crosslinked form. The degree of
crosslinking here may vary depending on the end use of the coatings
and on the crosslinkable components chosen. Typically, however, the
degree of crosslinking is between 5% and 100%, preferably between
35% and 100%, more preferably between 50% and 100%, with a degree
of crosslinking of 100% denoting complete crosslinking. However, a
degree of crosslinking of not more than 85% only may be desired or
achievable.
[0043] The degree of crosslinking here can be determined, in a way
which is known to the skilled worker, by means of various methods,
as for example by means of DMTA measurements (DMTA=dynamic
mechanical thermoanalysis). Dynamic mechanical thermoanalysis is a
widely known measurement method for determining the viscoelastic
properties of coatings, and is described, for example, in Murayama,
T., Dynamic Mechanical Analysis of Polymeric Material, Elsevier,
New York, 1978 and Loren W. Hill, Journal of Coatings Technology,
Vol. 64, No. 808, May 1992, pages 31 to 33.
[0044] The measurements can be conducted using, for example, the
Rheometrics Scientific DMTA V instrument, with a frequency of 1 Hz
and an amplitude of 0.2%, and with a heating rate of 2.degree. C.
per minute.
[0045] The spectroscopic detection of the absence of free
functional groups, such as analysis by IR spectroscopy, for
example, to show that there are no longer any free isocyanate
groups, can be employed, as is known, to detect that crosslinking
has taken place.
[0046] This crosslinking reaction may take place thermally and/or
by means of radiation and/or by means of moisture, but in
particular is accomplished thermally, together where appropriate
with moisture.
[0047] The coating (K) is obtainable from a coating composition (B)
which comprises at least two different crosslinkable components
(D1) and (D2). It is essential to the invention here that at least
part of component (D1) has one or more surface-active structural
units (O).
[0048] In the text below, the condition that at least part of
component (D1) has one or more surface-active structural units (O)
denotes the fact that, depending on the end use of the coatings and
on the crosslinkable components chosen, typically between 30% and
100%, preferably 50% and 100%, more preferably between 80% and
100%, and very preferably between 90% and 100% of component (D1)
have one or more surface-active structural units (O).
[0049] As a result of the surface-active structural units of the
crosslinkable component (D1) there is, in general, an accumulation
of component (D1) in the near-surface coating zone (K1), so that
generally, after curing of the coating composition (B), the
near-surface coating zone (K1) is formed substantially by the at
least partly crosslinked component (D1) and the volume coating zone
(K2) is formed substantially by the at least partly crosslinked
component (D2). "Substantially" in this context means that at least
50%, preferably at least 75%, and more preferably at least 90% by
weight of the respective zone (K1) or (K2) are formed from the
respective crosslinked component (D1) or (D2).
[0050] Owing to the accumulation of component (D1) in the
near-surface coating zone (K1), the at least partly crosslinked
coating (K) generally exhibits a chemical disuniformity in the form
of a gradient perpendicular to the surface (KO).
[0051] This gradient in the chemical disuniformity also leads
preferably to a gradient in the physical properties perpendicular
to the surface, preferably to a gradient in the scratch resistance
and/or stonechip resistance and/or crack resistance and/or
washability and/or refinish adhesion and/or wetting and/or optical
coloring and/or appearance.
[0052] In particular the at least partly crosslinked coating (K)
has a chemical disuniformity in the form of a gradient of silicon
atoms of type (Si 1) and/or of type (Si 2)
##STR00001##
perpendicular to the surface (KO), where
[0053] R.sup.S1=organic radical, preferably linear and/or branched
alkylene or cycloalkylene radical having 1 to 20 carbon atoms, more
particularly alkylene radical having 1 to 4 carbon atoms,
[0054] R''=alkyl, cycloalkyl, aryl or aralkyl, the carbon chain
possibly being interrupted by nonadjacent oxygen, sulfur or NRa
groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably
R''=alkyl radical, more particularly having 1 to 6 C atoms.
[0055] This gradient is produced in particular by a corresponding
selection of component (D1), preference being given to using
components (D1) which crosslink at least partly via alkoxysilane
groups. With very particular preference the gradient is obtained
via the use of the adducts (A) with silane functionality that are
described below.
[0056] The gradient preferably has a half-value depth <1 .mu.m,
more preferably <0.1 .mu.m, and very preferably <0.05 .mu.m.
This half-value depth is the depth or layer thickness of the at
least partly crosslinked coating at which the difference (i.e.,
gradient) in the chemical structure and/or in the physical
properties between surface (KO) and volume coating zone (K2) has
fallen to a half.
[0057] The crosslinking density in the near-surface zone (K1) is
generally higher than the crosslinking density in the volume
coating zone (K2).
[0058] It is assumed that, as a result of this, the at least partly
crosslinked coating (K) has a higher hardness, more particularly
micropenetration hardness, and a higher scratch resistance, more
particularly a higher dry scratch resistance, than a corresponding
coating (K') obtained from a coating composition (B') identical to
coating component (B) except for the fact that it contains no
crosslinkable component (D1). At the same time, the problems often
associated with improved scratch resistance, viz. increasing
brittleness and susceptibility to cracks, are avoided in the
coatings.
[0059] By way of the ratio of the crosslinking density of the
network (N1) formed from component (D1) to the crosslinking density
of the network (N2) formed from component (D2), therefore, it is
possible to exert targeted control over the properties of the
crosslinked coating (K).
Crosslinkable Component (D1)
[0060] The coating (K) is obtainable from a coating composition (B)
which comprises at least two different crosslinkable components
(D1) and (D2).
[0061] It is essential to the invention that at least part of
component (D1) has one or more surface-active structural units (O).
A surface-active structural unit, here and below, refers to
radicals which result in the components featuring this radical
accumulating copiously out of the coating composition (B) at the
air/coating interface.
[0062] In the coating compositions (B) of the invention,
accordingly, it is possible to use those components (D1) which from
the outset have surface-active structural units (O). A
surface-active structural unit is a reference here to radicals
which mean that the compounds carrying such a radical accumulate
copiously, out of the coating composition, at the air/coating
interface.
[0063] Use is made in particular, in accordance with the invention,
of coating compositions in which the crosslinkable component (D1)
has been prepared by modifying at least part of component (D1) with
one or more surface-active compounds (OV), the compounds (OV)
having the surface-active structural unit (O). Alternatively or
additionally it is also possible for at least part of a precursor
of component (D1) to have been modified with one or more
surface-active compounds (OV). Also possible is the simultaneous
reaction with the compound (OV) during the synthesis of the
component (D1) (in situ reaction, as it is known).
Surface-active Structural Unit (O)
[0064] The surface-active structural units (O) are preferably
selected from the group consisting of hydrocarbon radicals and
their derivatives, more particularly of fluorinated hydrocarbon
radicals, fatty acid radicals, and the radicals of fatty acid
derivatives, and also from the group consisting of unsubstituted or
substituted siloxane radicals, and more preferably from siloxane
radicals.
[0065] The surface-active compound (OV) preferably has at least one
hydroxyl, epoxy, isocyanate, carbamate, carboxyl, anhydride, amine
and/or thiol group and/or ethylenically unsaturated double bond,
and/or the crosslinkable component (D1) and/or a precursor of the
crosslinkable component (D1) has a complementary functional group
selected from the group consisting of hydroxyl, epoxy, isocyanate,
carbamate, carboxyl, anhydride, amine and/or thiol groups and/or
ethylenically unsaturated double bonds.
[0066] Use is made in particular of compounds (OV) which have a
lower surface tension than the nonmodified component (D1) or than
the synthesis components used to prepare component (D1). The
surface tension of the compound (OV) ought preferably to be at
least 1 mN/m and with particular preference at least 5 mN/m lower
than the surface tension of the nonmodified component (D1) or than
the surface tension of the synthesis components used to prepare
component (D1).
[0067] The measurement of this surface tension is made at a
temperature of 23.degree. C. The method used to determine the
surface tension was that known as the ring method. This involves
using a ring tensiometer, as it is known, to measure the maximum
force which acts on the periphery of a platinum ring when said ring
is extracted from the phase boundary of the liquid. The surface of
the liquid under investigation is slowly increased for the
measurement of the surface tension, the system always being in the
equilibrium state. The force needed to increase the surface area is
measured, and this measurement is converted to the surface tension.
A more detailed elucidation of the method is described in, among
other places, the book "Lackeigenschaften messen and steuern" by G.
Meichsner, Th. G. Mezger, J. Schroder, edited by Ulrich Zorll,
published by Vincentz Verlag 2003, page 96 ff.
[0068] The compound (OV) is preferably selected such that the
resulting component (D1) having the surface-active structural unit
(O) is surface-active in the coating composition. Surface-active
components (D1), here and below, are components (D1) which
accumulate copiously, out of the coating composition, at the
air/coating interface.
[0069] This accumulation of component (D1) at the air/coating
interface is typically achieved through the existence of a certain
incompatibility between component (D1) and the film-forming
material (D2). In turn, however, this incompatibility ought not to
be too high, in order to prevent flow defects on the part of the
coating composition. Furthermore, when using the surface-active
components (D1), it is necessary to take account of the other
physical limitations on the resulting paint formulation, and also
those of the substrate that is to be coated. One particularly
important aspect, besides adequate compatibility, is the wetting of
the target substrates, in particular. This wetting can be estimated
by methods including that of measuring the critical surface tension
according to Zismann. A detailed elucidation of this method is
described in literature, including the book "Lackeigenschaften
messen and steuern" by G. Meichsner, Th. G. Mezger, J. Schroder,
edited by Ulrich Zorll, published by Vincentz Verlag 2003.
Particular preference is given in this context to those components
(D1) which, on their own or in interaction with other
interface-active additives, make it possible to set a surface
tension for the respective paint formulation that is below the
critical surface tension for the particular target substrate.
[0070] Particularly preferred components (D1) are those which, on
their own or in interaction with other interface-active additives,
make it possible to set a surface tension of the respective paint
formulation that is at least 5 mN/m below the critical surface
tension for the particular target substrate.
[0071] As already remarked, compounds suitable as compounds (OV)
with low surface tension are those which have at least one
surface-active radical. More particularly the surface-active
radicals of the compound (O) are selected from the group consisting
of hydrocarbon radicals and their derivatives, such as the
fluorinated hydrocarbon radicals, the fatty acid radicals and their
derivatives, for example, and also from siloxane radicals and their
derivatives, such as the fluorinated siloxane radicals, for
example.
[0072] The surface-active hydrocarbon radicals are, more
particularly, linear or branched aliphatic chains which have
preferably at least 5 C atoms and more preferably 12 to 36 C atoms
and which may if appropriate also carry corresponding substituents,
such as fluorine radicals, for example. With regard to the higher
homologs, branched structures or structures which as a result of
functionalizations do not display crystallization at room
temperature are preferred.
[0073] Examples of compounds used as compound (OV) with a
hydrocarbon radical are, more particularly, alkanes, alkenes, and
alkynes and also their derivatives which in addition have at least
one functional group as well.
[0074] Besides the monofunctional building blocks it is also
possible to use compounds (OV) having a functionality of two or
more.
[0075] Examples of compounds having a relatively low surface
tension, which are reactive in relation to the nonmodified
component (D1), are, in particular, aliphatic alcohols, fatty acids
and fatty acid derivatives having in each case linear or branched
aliphatic chains having in general at least 5 C atoms and
preferably having 12 to 36 C atoms. Particular preference is given
to linear and/or branched fatty acid derivatives having 12-36 C
atoms.
[0076] Preference is given very generally to the saturated
compounds (OV). The reason for this is the high weathering
stability the resulting coatings must guarantee.
[0077] Examples of possible such compounds include octanol,
nonanol, decanol, undecyl alcohol, dodecyl alcohol, and the
correspondingly higher homologs. Owing to the relatively low
crystallization tendency, preference is given to the use, for
example, of isostearyl alcohol (available, for example, under the
trade name Isofol from Condea) over the use of n-stearyl
alcohol.
[0078] Examples of difunctional starting materials include isomers
of dihydroxyoctane, isomers of dihydroxynonane, isomers of
dihydroxydecane, isomers of dihydroxyundecane, and correspondingly
higher homologs.
[0079] Also suitable as surface-active building blocks are the
derivatives of saturated and/or unsaturated fatty acids, more
particularly those of saturated and/or unsaturated fatty acids
having 5 to 30 carbon atoms in the molecule, such as radicals of
valeric acid, caproic acid, enanthic acid, caprylic acid,
pelargonic acid, capric acid, undecylic acid, lauric acid, myristic
acid, palmitic acid, stearic acid, oleic acid, elaidic acid,
arachidic acid, behenic acid, lignoceric acid, cerotic acid,
melissic acid, linoleic acid, ricinenic acid, ricinoleic acid,
linolenic acid, arachidonic acid, clupanodonic acid,
alpha-eleostearic acid, alpha-licanic acid, alpha-parinaric acid,
ricinoleic acid and isanolic acid and mixtures of these fatty
acids, and/or the corresponding hydroxy acids of the stated fatty
acids, and/or mixtures thereof. Thus as surface-active compound
(OV) it is also possible to use hydroxyvaleric acid, hydroxycaproic
acid, hydroxystearic acid, hydroxylauric acid, ricinoleic acid or
mixtures thereof.
[0080] Also suitable, furthermore, are the corresponding radicals
of dimer and trimer fatty acids and also mixtures thereof. Mention
may be made here, by way of example, of dimer fatty acid diols.
They are available commercially, for example, under the designation
Pripol.RTM. from the company Unichema. They can be prepared by
reducing the corresponding dimer fatty acids, as described for
example in Karlheinz Hill, "Fats and Oils as Oleochemical Raw
Materials," Pure Appl. Chem., Vol. 72, No. 7, pages 1255-1264
(2000), more particularly page 1261. Suitable, for example, is the
commercially available PRIPOL 2033 from Unichema North America,
Chicago, Ill., USA.
[0081] Epoxidized fatty acids as well can be used as reation
partners for anhydride-functional nonmodified components (D1).
[0082] Other examples of corresponding compounds (OV) having a
hydrocarbon radical as surface-active radical are amine-functional
compounds of low surface tension.
[0083] As examples of such compounds mention may be made of
octylamine, nonylamine, decylamine, undecylamine, dodecylamine, and
the correspondingly higher homologs.
[0084] Besides the monofunctional building blocks it is also
possible to use compounds (OV) having a functionality of two or
more. Examples of difunctional starting materials include isomers
of diaminooctane, isomers of diaminononane, isomers of
diaminodecane, isomers of diaminoundecane, and corresponding higher
homologs.
[0085] Besides the amine-functional compounds (OV) it is also
possible to employ the corresponding mercapto-functional
derivatives.
[0086] Furthermore it is also possible in particular to employ
isocyanate-functional fatty acid derivatives as compounds (OV). An
example that may be mentioned here is stearyl isocyanate, which can
be employed, for example, as a reaction partner with nonmodified
components (D1) possessing secondary-amine functionality.
[0087] In cases requiring a particularly low surface tension on the
part of modified component (D1) use is also made, preferably, of
organic substances with fluorinated side chains, more particularly
fluorinated hydrocarbons. Examples of such compounds are the
methacrylates with fluorinated side chains, which can be reacted in
Michael addition reactions with amine-functional nonmodified
components (D1) or else 3-fluorobenzyl alcohol as an OH-functional
component. Furthermore, however, it is also possible to employ
other fluorinated substances of low surface tension that are
reactive toward the corresponding silanes.
[0088] For the reaction with Si--H groups it is also possible to
employ various unsaturated oligomers and polymers as compounds
(OV). Particularly preferred for use are 1,2-polybutadienes and
also various copolymers of 1,2-polybutadienes. In addition it is
possible to employ polyisobutylenes having terminal double bonds.
Use may also be made, furthermore, of surface-active grafted
polymers or grafted polymers with ethylenically unsaturated double
bonds in the side chains.
[0089] As compound (OV) it is also possible, furthermore, to employ
siloxanes or their derivatives.
[0090] Suitability is possessed in principle by all polysiloxanes
which have on average at least one functional group which is
reactive with the complementary functional groups of the
nonmodified component (D1). Use is made in particular of
polysiloxanes which have at least one hydroxyl, carboxyl, amine
and/or thiol group, vinyl, isocyanate and/or epoxy group, more
particularly glycidyl group, and/or anhydride group and/or acryloyl
and methacryloyl group, more particularly at least one hydroxyl,
carboxyl, amine and/or thiol group.
[0091] Suitability is possessed for example by polysiloxanes of the
formula (I)
##STR00002##
where
[0092] R.sup.1 to R.sup.6 are identical or different radicals
and
[0093] R.sup.1=alkyl, cycloalkyl, aryl or aralkyl radical, the
carbon chain possibly being interrupted by nonadjacent oxygen,
sulfur or NRa groups, or fluorine-substituted alkyl, cycloalkyl,
aryl or aralkyl radicals, preference being given to structures
which have an ethylene radical between the silicon atom and the
fluorine-substituted organic radical,
[0094] R.sup.2=hydroxyl, alkyl, cycloalkyl, aryl or aralkyl
radical, the carbon chain possibly being interrupted by nonadjacent
oxygen, sulfur or NRa groups,
[0095] R.sup.3 and R.sup.6=hydrogen, alkyl, cycloalkyl, aryl or
aralkyl radical, the carbon chain possibly being interrupted by
nonadjacent oxygen, sulfur or NRa groups, or fluorine-substituted
alkyl, cycloalkyl, aryl or aralkyl radicals, preference being given
to structures which have an ethylene radical between the silicon
atom and the fluorine-substituted organic radical,
[0096] R.sup.4 and R.sup.5=hydrogen, hydroxyl, alkyl, cycloalkyl,
aryl or aralkyl radical, the carbon chain possibly being
interrupted by nonadjacent oxygen, sulfur or NRa groups,
[0097] at least one of the radicals R.sup.2, R.sup.4, and R.sup.5
additionally carrying a functional group which is reactive toward
the complementary functional groups of component (D1),
and
[0098] m.sub.1=1 to 80, preferably 3 to 20, and
[0099] m.sub.2=0 to 80, preferably 0 to 10.
[0100] With preference here the functional group is in each case
selected from hydroxyl, carboxyl, amine and/or thiol groups, vinyl,
isocyanate and/or epoxy groups, more particularly glycidyl groups,
and anhydride groups, and also acryloyl and methacryloyl
groups.
[0101] Varying the molecular weight of the respective siloxane
chains allows targeted variation in the compatibility of the
resulting component (D1) with the coating compositions. To obtain
high compatibility with the coating compositions, particular
preference is given to using siloxanes (OV) of comparatively low
molecular weight. These siloxanes are also described in, for
example, the application US 20040209088, paragraphs [0017] to
[0019], and are explicitly likewise mentioned as preferred
ingredients.
[0102] In principle the molecular weight of the siloxane employed
as compound (OV) may be adapted in accordance with the anticipated
compatibility with the coating compositions that are to be
modified. However, it has been found that, in many cases, low
molecular weights tend to exhibit high compatibility. In light of
this, accordingly, preference is given to low molecular weights,
which are reflected in the preferred degrees of polymerization
m.sub.1 and m.sub.2.
[0103] With regard to the nonfunctional substituents on the
respective silicon atoms within the siloxane chain it is likewise
possible to make variations in accordance with the anticipated
compatibility of the components with the coating compositions that
are to be modified. In order to lower the surface tension in a
targeted way and hence to obtain the inventive components (D1), it
is preferred as nonfunctional radicals to use methyl, ethyl and
phenyl radicals and also alkyl radicals which are partly
substituted by fluorine. Particular preference is given to using
the methyl radical as a nonfunctional radical.
[0104] In order to make the silanes more compatible in a targeted
way it is also possible to introduce oligomers or polymers of
ethylene oxide or of propylene oxide as side chains.
[0105] Preference is given to using polysiloxanes of the formula
(II):
##STR00003##
where
[0106] R.sup.1, R.sup.4 and R.sup.5 are as defined above and
[0107] m=1 to 80, preferably 3 to 20 and more preferably 5 to
12.
[0108] Examples of siloxanes with surface-active compound
suitability include the compounds specified in paragraphs [0012] to
[0018] of the patent application US 20040209088.
[0109] In particular, carbinol-functional siloxanes of the
abovementioned formula (II) are employed.
[0110] Examples of siloxanes with hydroxyl groups that are suitable
as compound (OV) are carbinol-terminated
dimethylsiloxane-caprolactone block copolymers (available
commercially from ABCR GMBH & CO. KG, Karlsruhe, under article
number AB127698), carbinol-functional
methyl-siloxane-dimethylsiloxane copolymer (available commercially
from ABCR GMBH & CO. KG, Karlsruhe, under article numbers
AB127701 and AB127700), carbinol-terminated polydimethylsiloxane
(available commercially from ABCR GMBH & CO. KG, Karlsruhe,
under article number AB153380), monocarbinol-terminated
polydimethylsiloxanes (available commercially from ABCR GMBH &
CO. KG, Karlsruhe, under article numbers AB127710 and AB109345 and
AB146681 and AB146683 and AB146682), and more particularly the
carbinol-functional siloxanes.
[0111] Very particular preference is given to functional siloxanes
with a symmetric structure, of the formula (III) below:
##STR00004##
where
[0112] R.sup.1 and R.sup.4 are as defined above and preference is
given to methyl, ethyl, and phenyl radicals and also to alkyl
radicals partly substituted by fluorine and/or the functional
group. Particular preference is given to using the methyl radical
as nonfunctional radical, and/or the functional group is preferably
a hydroxyl group.
[0113] m=1 to 80, preferably 3 to 20, and more preferably 5 to
12.
[0114] Very particular preference is given to using siloxanes of
the formula (III) where R.sup.4 contains a hydroxyl group. It is
preferred to use the carbinol-functional polysiloxane
Baysilone.RTM. OF 502 from GE Bayer Silicones. The material is
available in various molecular weights, e.g., Baysilone.RTM. OF 502
6% and Baysilone.RTM. OF 502 3%. Preferred in this context is the
material Baysilone.RTM. OF 502 6%, which has a lower molecular
weight.
[0115] Furthermore, siloxanes with primary or secondary amine
functions, in accordance with the formula (II) or (III), are
employed with particular preference, an example being
aminopropylmethylsiloxane-dimethylsiloxane copolymer (available
commercially from ABCR GMBH & CO. KG, Karlsruhe, under article
numbers AB109374 and AB109373 and AB109375).
Adducts (A) with Silane Functionality
[0116] As crosslinkable groups, component (D1) preferably contains
hydrolyzable silane groups, more particularly alkoxysilane groups,
since these groups, when component (D1) is crosslinked, form a
dense Si--O--Si-- network of high scratch resistance that ensures
the outstanding properties of the resulting coatings. These
components (D1) also lead to the aforementioned gradients of
silicon atoms of type (Si 1) and/or (Si 2) in the at least partly
crosslinked coating (K) perpendicular to the surface (KO).
[0117] Particular preference is given in accordance with the
invention to the use as component (D1) of adducts (A) with silane
functionality which are preparable by an addition reaction of
[0118] (a) at least one silane (S1) which has at least one
functional group which is reactive with the complementary
functional groups of the compound (OV) and [0119] (b) at least one
compound (OV) which has at least one complementary functional group
and at least one surface-active radical.
[0120] By addition reaction here is meant nucleophilic,
electrophilic, pericyclic or metal-catalyzed addition reactions, of
the kind whose mechanisms are also described in the textbooks of
organic chemistry, among other references, an example being
Organikum, "Reaktionsmechanismen in der Organischen Chemie", Peter
Sykes, VCH-Verlag, in detail.
[0121] These addition reactions for preparing the adducts (A) with
silane functionality are employed in particular for the reaction of
the silane (S1) with the compound (OV). It is, however, also
possible, in addition, first to synthesize the silanes (S1) by
means of a corresponding addition reaction, and only then to carry
out the reaction with the compound (OV). It is preferred to
synthesize the silanes (S1) in situ by means of a corresponding
addition, while at the same time the reaction with the compound
(OV) is carried out.
[0122] Functional groups of the silanes (S1) and/or the functional
groups of the compound (OV) are preferably selected from the group
consisting of hydroxyl, epoxy, isocyanate, carbamate, carboxyl,
anhydride, amine, and thiol groups and/or ethylenically unsaturated
double bonds.
[0123] It is preferred, furthermore, for the functional groups of
the silanes and of the compound (OV) not both simultaneously to be
ethylenically unsaturated double bonds, but instead for only one of
the two groups to be an ethylenically unsaturated double bond.
[0124] Moreover, it is preferred in the coating compositions of the
invention to employ adducts (A) which contain on average less than
50 mol % of free reactive groups other than the silane groups, more
particularly than the alkoxysilane groups.
[0125] Examples of suitable addition reactions for preparing the
adducts (A) with silane functionality therefore include more
particularly [0126] (I) reactions of isocyanate groups with
hydroxyl groups, of isocyanate groups with amino groups, and of
isocyanate groups with thiol groups; [0127] (II) reactions of epoxy
groups with carboxyl groups and of epoxy groups with anhydride
groups; [0128] (III) reactions of compounds containing active
hydrogen atoms on ethylenically unsaturated double bonds (known as
Michael additions), more particularly additions of amino groups
with ethylenically unsaturated double bonds; and [0129] (IV)
metal-catalyzed addition reactions.
[0130] Examples of reactions of group (I) include the following
reactions: [0131] additions of isocyanate-functional compounds with
aminosilanes, [0132] additions of isocyanate-functional compounds
with thiol-functional silanes, [0133] additions of
isocyanatosilanes with hydroxy-functional compounds, [0134]
additions of isocyanatosilanes with amine-functional compounds, and
[0135] additions of isocyanatosilanes with thiol-functional
compounds.
[0136] Inventively preferred is the nucleophilic addition of
amine-functional silanes or thiol-functional silanes with
isocyanate-functional oligomers.
[0137] Here and below an oligomer is a compound which has in
general on average 2 to 10 basic structures or monomer units. A
polymer, in contrast, is a compound which has in general on average
more than 10 basic structures or monomer units.
[0138] Examples of reactions of group (II) include the following
reactions: [0139] additions of epoxy-functional silanes with
carboxy-functional compounds, [0140] additions of epoxy-functional
silanes with anhydride-functional compounds, and [0141] additions
of anhydride-functional silanes with epoxy-functional
compounds.
[0142] An exhaustive description of the addition reaction of the
anhydride-functional silanes with epoxy-functional compounds is
found in WO 2006/097387.
[0143] Examples of reactions of group (III) include the following
reactions: [0144] additions of aminosilanes with
alpha,beta-unsaturated compounds, e.g., acryloyl- and
methacryloyl-functional compounds, such as di(meth)acrylates, and
the like.
[0145] Mention may be made here, by way of example, of group (IV),
namely the metal-catalyzed addition reactions, of the
hydrosilylation reaction. In the context of a hydrosilylation
reaction of this kind it is possible, for example, for silanes with
Si--H functionality to be reacted with (poly)olefins or with
siloxanes containing C.dbd.C double bonds, such as
diphenylsiloxane-dimethylsiloxane-vinyl-terminated copolymer, for
example, which is available commercially from ABCR GmbH & Co.
KG under article number AB 116641.
[0146] Other metal-catalyzed addition reactions as well, however,
more particularly coupling reactions, can be employed.
[0147] Very generally it is possible as silanes (S1) to use
compounds containing Si--H groups. These compounds can be reacted
in a hydrosilylation reaction with the compounds (OV).
[0148] Mention may be made by way of example of silanes (S1) of
this kind, containing Si--H groups, of trichlorosilane,
methyldichlorosilane, and dimethylchlorosilane.
[0149] Compounds of this kind can be reacted with unsaturated
compounds such as, for example, various 1,2 oligobutadienes or
polybutadienes, or with siloxanes containing double bonds, such as
under platinum catalysis, for example, to give the corresponding
silane-functional resins. Where appropriate these silanes (S1)
containing Si--H groups can be reacted in a reaction with suitable
alcohols, such as methanol, to give the corresponding
alkoxysilanes.
[0150] As well as the silanes containing Si--H bond it is
particularly preferred to use organofunctional silanes (S1).
Organofunctional silanes which can be used are silanes having one
hydrolyzable radical, having two, or having three or more
hydrolyzable radicals. With regard to the compatibility and the
reactivity of the silanes, however, silanes having at least 3
hydrolyzable radicals are employed with preference.
[0151] Very generally the inventively preferred organofunctional
silanes (S1) can be represented by the structural formula (IV)
R.sup.S.sub.n--Si--R''.sub.xX.sub.4-(n+x) (IV).
[0152] The groups X, which may be identical or different, are
hydrolyzable groups.
[0153] The groups R.sup.S represent organic radicals having at
least one functional group, more particularly linear and/or
branched alkylene or cycloalkylene radicals having 1 to 20 carbon
atoms and having at least one functional group, especially alkylene
radicals having 1 to 4 carbon atoms and having at least one
functional group;
[0154] R'' is alkyl, cycloalkyl, aryl or aralkyl, the carbon chain
possibly being interrupted by nonadjacent oxygen, sulfur or NRa
groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably
R''=alkyl radical, more particularly having 1 to 6 C atoms.
[0155] In the structural formula, n=1 to 3, preferably 1 to 2, more
preferably n=1, x=0 to 2, preferably 0 to 1, more preferably x=0,
and 1.ltoreq.n+x.ltoreq.3, preferably 1.ltoreq.n+x.ltoreq.2, more
preferably n+x=1.
[0156] The hydrolyzable groups X can be selected from the group of
halogens, more particularly chlorine and bromine, from the group of
alkoxy groups, from the group of alkylcarbonyl groups, and from the
group of acyloxy groups. Alkoxy groups are particularly
preferred.
[0157] The alkoxysilanes employed with particular preference can
therefore be represented by the formula (V)
R.sup.S.sub.n--Si--R''.sub.x(OR).sub.4-(n+x) (V)
where n=1 to 3, preferably n=1 to 2, and more preferably n=1, x=0
to 2, preferably 0 to 1, more preferably x=0, and
1.ltoreq.n+x.ltoreq.3, preferably 1.ltoreq.n+x.ltoreq.2, more
preferably n+x=1, and R.sup.S and R'' are as defined for formula
(IV).
[0158] The radical R may be hydrogen, alkyl or cycloalkyl, the
carbon chain possibly being interrupted by nonadjacent oxygen,
sulfur or NRa groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl,
preferably R=alkyl radical, more particularly having 1 to 6 C
atoms.
[0159] The respective preferred alkoxy radicals may be alike or
different; what is critical for the structure of the radicals,
however, is to what extent they influence the reactivity of the
hydrolyzable silane groups. Preferably R is an alkyl radical, more
particularly having 1 to 6 C atoms. Particularly preferred are
radicals R which raise the reactivity of the silane groups, i.e.,
which represent good leaving groups. Consequently a methoxy radical
is preferred over an ethoxy radical, which in turn is preferred
over a propoxy radical. With particular preference, therefore,
R=ethyl and/or methyl, more particularly methyl. Very generally,
however, less-reactive silanes than (S1) can also be employed. In
these cases it is necessary to achieve a sufficient crosslinking
density either by means of a correspondingly more efficient
catalyst, or else a correspondingly higher amount of catalyst must
be added.
[0160] Nonfunctional substituents on the organofunctional silane
(S1), more particularly substituents on the radical R.sup.S, may
also influence its reactivity. This may be illustrated by way of
example taking as an example bulky voluminous substituents on the
amine function, which are able to reduce the reactivity of
amine-functional silanes. Against this background,
N-(n-butyl)-3-aminopropyltrimethoxysilane is preferred before
N-cyclohexyl-3-aminopropyltrimethoxysilane.
[0161] Very generally, the radicals R.sup.S which raise the
reactivity of the silanes are preferred over radicals which lower
the reactivity of the silanes.
[0162] The reactivity of organofunctional silanes can also be
significantly influenced, furthermore, through the length of the
spacers or radicals R.sup.S1 between silane functionality and
organic functional groups. As examples of this, mention may be made
of the "alpha" silanes, which are available from Wacker, and in
which there is a methylene group, instead of the propylene group
present in the case of "gamma" silanes, between Si atom and
functional group. To illustrate this it is observed that
methacryloyloxymethyltrimethoxysilane ("alpha" silane, e.g.,
commercial product GENIOSIL.RTM. XL 33 from Wacker) is used with
preference over methacryloyloxypropyltrimethoxysilane ("gamma"
silane, e.g., commercial product GENIOSIL.RTM. GF 31 from Wacker)
for the synthesis of the adducts (A) of the invention.
[0163] Very generally, spacers which raise the reactivity of the
silanes are preferred over spacers which lower the reactivity of
the silanes.
[0164] In order to achieve as high as possible a crosslinking
density through silane crosslinking it is advantageous to realize
as many silane groups as possible in relation to the molecular
weight of the adduct that is to be employed. If this has been
ensured, and a particularly high network density results in the
solid film, particularly good properties can be achieved in
respect, among other things, of the scratch resistance. Against
this background, very particular preference is given to those
organofunctional silanes which allow a particularly high
functionality to be realized in the resin with virtually no notable
increase in molecular weight.
[0165] This may be shown by way of example taking as an example two
amine-functional silanes: bis(3-trimethoxysilylpropyl)amine is
preferred in front of
N-(n-butyl)-3-aminopropyltrimethoxysilane.
[0166] The reactive groups of the silanes (S1) are preferably
selected from the group consisting of amine, epoxy, anhydride,
isocyanate, carbamate and/or thiol groups and/or ethylenically
unsaturated double bonds.
[0167] Listed below by way of example--but without limitation--are
inventively preferred organofunctional silanes which are
particularly suitable for the preparation of the adducts (A):
1) Amine-Functional and Thiol-Functional Silanes.
[0168] Use is made, especially in the context of Michael additions,
of, for example, primary aminosilanes, such as
3-aminopropyltriethoxysilane (available for example under the brand
name Geniosil.RTM. GF 93 from Wacker Chemie),
3-aminopropyltrimethoxysilane (available for example under the
brand name Geniosil.RTM. GF 96 from Wacker Chemie),
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (available for
example under the brand name Geniosil.RTM. GF 9 and also
Geniosil.RTM. GF 91 from Wacker Chemie),
N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane (available for
example under the brand name Geniosil.RTM. GF 95 from Wacker
Chemie) and the like.
[0169] Use is made, particularly in the context of additions to
isocyanate-functional compounds, of, for example, secondary
aminosilanes and mercapto-functional silanes, such as, for example,
bis(2-tri-methoxysilylethyl)amine, bis(2-triethoxysilylethyl)amine,
bis(3-triethoxy-silylpropyl)amine (available under the trade name
Dynasylan.RTM. 1122 from Degussa),
bis(3-trimethoxysilylpropyl)amine (available under the trade name
Dynasylan.RTM. 1124 from Degussa),
bis(4-triethoxysilyl-butyl)amine,
N-(n-butyl)-3-aminopropyltrimethoxysilane (available under the
trade name Dynasylan.RTM. 1189 from Degussa),
N-(n-butyl)-3-aminopropyltriethoxysilane,
N-cyclohexyl-3-aminopropyltrimethoxysilane (available under the
brand name Geniosil.RTM. GF 92 from Wacker Chemie),
N-cyclohexyl-3-aminopropyltriethoxysilane,
3-mercaptopropyl-trimethoxysilane (available from Degussa under the
trade name Dynasylan.RTM. MTMO), 3-mercaptopropyltriethoxysilane,
N-cyclo-hexylaminomethylmethyldiethoxysilane (available from Wacker
Chemie under the trade name Geniosil.RTM. XL 924),
N-cyclohexylaminomethyl-triethoxysilane (available from Wacker
Chemie under the trade name Geniosil.RTM. XL 926),
N-phenylaminomethyltrimethoxysilane (available from Wacker Chemie
under the trade name Geniosil.RTM. XL 973), and the like.
2) Epoxy-Functional Silanes
[0170] Epoxy-functional silanes can be used in particular for
addition to carboxylic acid-functional or anhydride-functional
compounds. Examples of suitable epoxy-functional silanes are
3-glycidyloxypropyltrimethoxysilane (available from Degussa under
the trade name Dynasylan.RTM.GLYMO),
3-glycidyloxypropyltriethoxysilane (available from Degussa under
the trade name Dynasylan.RTM. GLYEO), and the like.
3) Anhydride-Functional Silanes
[0171] Anhydride-functional silanes can be used in particular for
addition to epoxy-functional compounds. An example that may be
mentioned of a silane with anhydride functionality is
3-(triethoxysilyl)propylsuccinic anhydride (available from Wacker
Chemie under the trade name Geniosil.RTM. GF 20).
4) Silanes with Ethylenically Unsaturated Double Bonds
[0172] Silanes of this kind can be used in the context of Michael
reactions or else in the context of metal-catalyzed reactions.
Those exemplified are 3-methacryloyloxypropyltrimethoxysilane
(available for example from Degussa under the trade name
Dynasilan.RTM. MEMO, or from Wacker Chemie under the trade name
Geniosil.RTM. GF 31), 3-methacryloyloxy-propyltriethoxysilane,
vinyltrimethoxysilane (available from, among others, Wacker Chemie
under the trade name Geniosil.RTM. XL 10),
vinyl-dimethoxymethylsilane (available from, among others, Wacker
Chemie under the trade name Geniosil.RTM. XL 12),
vinyltriethoxysilane (available from, among others, Wacker Chemie
under the trade name Geniosil.RTM. GF 56),
(methacryloyloxymethyl)methyldimethoxysilane (available from, among
others, Wacker Chemie under the trade name Geniosil.RTM. XL 32),
methacryloyloxymethyltrimethoxysilane (available from, among
others, Wacker Chemie under the trade name Geniosil.RTM. XL 33),
(methacryloyloxymethyl)methyldiethoxysilane (available from, among
others, Wacker Chemie under the trade name Geniosil.RTM. XL 34),
and methacryloxymethyltriethoxysilane (available from, among
others, Wacker Chemie under the trade name Geniosil.RTM. XL
36).
5) Silanes with Isocyanate Function or Carbamate Function
[0173] Silanes with isocyanate function or carbamate function are
employed in particular in the context of reactions with
hydroxyl-functional compounds. Examples of silanes with isocyanate
function are, for example, described in the as yet unpublished
American patent application bearing the Ser. No. 11/227,867.
[0174] Examples of suitable isocyanatoalkyltrialkoxysilanes are
isocyanatopropyltrimethoxysilane,
isocyanatopropylmethyldimethoxysilane,
isocyanatopropylmethyldiethoxysilane,
isocyanatopropyltriethoxysilane,
isocyanatopropyltriisopropoxysilane,
isocyanatopropylmethydiiso-propoxysilane;
isocyanatoneohexyltrimethoxysilane,
isocyanato-neohexyldimethoxysilane,
isocyanatoneohexyldiethoxysilane,
isocyanatoneohexyltriethoxysilane,
isocyanatoneohexyltriisoprop-oxysilane,
isocyanatoneohexyldiisopropoxysilane,
isocyanatoisoamyl-trimethoxysilane,
isocyanatoisoamylmethyldimethoxysilane,
isocyanato-isoamylmethyldiethoxysilane,
isocyanatoisoamyltriethoxysilane,
iso-cyanatoisoamyltriisopropoxysilane, and
isocyanatoisoamylmethyldiiso-propoxysilane. Many
isocyanatoalkyltri- and -di-alkoxysilanes are available
commercially, for example, under the designation SILQUEST.RTM. from
OSi Specialties, Inc., a Witco Corporation company.
[0175] The isocyanatopropylalkoxysilane used preferably has a high
degree of purity, more particularly a purity of at least 95%, and
is preferably free from additives, such as transesterification
catalysts, which can lead to unwanted side reactions.
[0176] Use is made in particular of
(isocyanatomethyl)methyldimethoxysilane (available from Wacker
Chemie under the brand name Geniosil.RTM. XL 42),
3-isocyanatopropyltrimethoxysilane (available from Wacker Chemie
under the brand name Geniosil.RTM. XL 40) and
N-dimethoxy(methyl)silyl-methyl O-methylcarbamate (available from
Wacker Chemie under the brand name Geniosil.RTM. XL 65).
[0177] As silane component (S1) for reaction with the compound (OV)
it is also possible, instead of or together with these monomeric
silanes containing at least one functional group, to use adducts
which have at least one functional group and at least one
alkoxysilane group. These adducts with suitability as component
(S1) are preparable by an addition reaction of the silanes having
at least one, in particular more than one, functional group and a
compound (V2) which contains at least one, preferably at least two,
complementary functional group(s) (G2) which are reactive with
functional groups of the silane. Use is made in particular of
adducts of this kind as silane component (S1), in order to increase
the alkoxy functionality without a substantial increase in
molecular weight. Preferably, therefore, the compounds (V2) have a
number-average molecular weight below 1000, more particularly below
500.
[0178] It is preferred to synthesize the adducts employed as
silanes (S1) by means of a corresponding addition reaction in situ,
while at the same time the reaction is carried out with the
compound or compounds (OV). Suitable addition reactions are the
addition reactions already mentioned above.
[0179] Besides this, however, it is also conceivable first to react
the compound or compounds (OV) with a compound (V1) which contains
at least one, preferably at least two, complementary functional
group(s) which are reactive with the functional groups of the
compound (OV). This reaction can take place before the reaction
with the silane (S1). However, it is preferably carried out in
situ, i.e., while the reaction with the silane (S1) is taking place
at the same time. The compounds (V1) preferably have a
number-average molecular weight below 1000, more particularly below
500.
[0180] One option for an in situ process of this kind encompasses
the incomplete reaction of an isocyanate, more particularly of a
diisocyanate or polyisocyanate, with one or more compounds (OV)
which contain secondary amino groups or hydroxyl groups. The
remaining isocyanate groups can then be reacted with suitable
organofunctional silanes. It is preferred for this purpose to use
silanes having secondary amine functions, although all other
silanes that are reactive toward isocyanates can also be
employed.
[0181] Components (D1) employed with particular preference in the
coating compositions of the invention are obtainable by means of an
in situ process which embraces the incomplete reaction of an
isocyanate, more particularly a diisocyanate or polyisocyanate,
with one of the abovementioned surface-active compounds containing
secondary amine groups or hydroxyl groups. The remaining isocyanate
groups can then be reacted with suitable organofunctional silanes.
For this purpose it is preferred to use silanes containing
secondary amine functions, although all other organofunctional
silanes that are reactive toward isocyanates can also be
employed.
[0182] Very particular preference is therefore given to the use as
component (D1) of compounds which contain at least one reactive
radical of the formula (VI):
--NR'''--C(O)--N-(L-SiR''x(OR')3-x)n(L'-SiR''y(OR')3-y)m (VI)
where
[0183] R'''=hydrogen, alkyl, cycloalkyl, aryl or aralkyl, the
carbon chain possibly being interrupted by nonadjacent oxygen,
sulfur or NRa groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl
and
[0184] R'=hydrogen, alkyl or cycloalkyl, the carbon chain possibly
being interrupted by nonadjacent oxygen, sulfur or NRa groups, with
Ra=alkyl, cycloalkyl, aryl or aralkyl,
[0185] L, L'=linear and/or branched alkylene or cycloalkylene
radical having 1 to 20 carbon atoms, more particularly alkylene
radical having 1 to 4 carbon atoms, especially L, L'=R.sup.S1 of
the formulae (Si 1) or (Si 2),
[0186] R''=alkyl, cycloalkyl, aryl or aralkyl, the carbon chain
possibly being interrupted by nonadjacent oxygen, sulfur or NRa
groups,
[0187] n=0 to 2, m=0 to 2, m+n=2,
and
[0188] x, y=0 to 2.
[0189] These preferred components (D1) of the invention, containing
at least one reactive radical of the formula (VI), have preferably
been prepared by reaction of [0190] at least one di- and/or
polyisocyanate (PI) with [0191] at least one aminosilane of the
formula (VII)
[0191] H--N-(L-SiR''x(OR')3-x)n(L'-SiR''y(OR')3-y)m (VII), [0192]
where the substituents R', L, L', and R'' and the indices n, m, x,
and y are as defined for the formula (VI), and [0193] at least one
surface-active compound (OV).
[0194] Particularly preferred aminosilanes (VII) are
bis(2-ethyltrimethoxysilyl)-amine,
bis(3-propyltrimethoxysilyl)amine,
bis(4-butyltrimethoxy-silyl)amine, bis(2-ethyltriethoxysilyl)amine,
bis(3-propyltriethoxysilyl)-amine and/or
bis(4-butyltriethoxysilyl)amine. Bis(3-propyltrimethoxysilyl)-amine
is especially preferred. Aminosilanes of this kind are available
for example under the brand name DYNASILAN.RTM. 1124 from DEGUSSA
or Silquest.RTM. from OSI Specialties Inc.
[0195] Suitable di- and/or polyisocyanates (PI) for the preparation
of this component (D1) are substituted or unsubstituted aromatic,
aliphatic, cycloaliphatic and/or heterocyclic di- and/or
polyisocyanates that are known per se. Examples of preferred di-
and/or polyisocyanates include the following: 2,4-toluene
diisocyanate, 2,6-toluene diisocyanate, diphenylmethane
4,4'-diisocyanate, diphenylmethane 2,4'-diisocyanate, p-phenylene
diisocyanate, biphenyl diisocyanates,
3,3'-dimethyl-4,4'-diphenylene diisocyanate, tetramethylene
1,4-diisocyanate, hexamethylene 1,6-diisocyanate,
2,2,4-trimethylhexane 1,6-diisocyanate, isophorone diisocyanate,
2-isocyanatopropylcyclohexyl isocyanate, dicyclohexylmethane
2,4'-diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, 1,4- or
1,3-bis(isocyanatomethyl)cyclohexane, 1,4- or 1,3- or
1,2-diisocyanatocyclohexane, 2,4- or 2,6-diisocyanato
1-methyl-cyclohexane, diisocyanates derived from dimer fatty acids,
of the kind sold under the commercial designation DDI 1410 by
Henkel, ethylene diisocyanate, 1,12-dodecane diisocyanate,
cyclobutane 1,3-diisocyanate, cyclohexane 1,3-diisocyanate,
cyclohexane 1,4-diisocyanate, methylcyclohexyl diisocyanates,
hexahydrotoluene 2,4-diisocyanate, hexahydrotoluene
2,6-diisocyanate, hexahydrophenylene 1,3-diisocyanate,
hexahydrophenylene 1,4-diisocyanate, perhydrodiphenylmethane
2,4'-diisocyanate, 4,4'-methylenedicyclohexyl diisocyanate (e.g.,
Desmodur.RTM. W from Bayer AG), tetramethylxylyl isocyanates (e.g.,
TMXDI.RTM. from American Cyanamid), and mixtures of the
aforementioned polyisocyanates. Preferred polyisocyanates,
furthermore, are the biuret dimers and the isocyanurate trimers of
the aforementioned diisocyanates.
[0196] Particularly preferred polyisocyanates (PI) are
hexamethylene 1,6-diisocyanate, isophorone diisocyanate, and
4,4'-methylenedicyclohexyl diisocyanate, their biuret dimers and/or
isocyanurate trimers.
[0197] In another embodiment of the invention the polyisocyanates
(PI) are polyisocyanate prepolymers with urethane structural units,
which are obtained by reacting polyols with a stoichiometric excess
of aforementioned polyisocyanates. Polyisocyanate prepolymers of
this kind are described for example in U.S. Pat. No. 4,598,131.
[0198] Especially preferred components (D1) are reaction products
of hexamethylene 1,6-diisocyanate and isophorone diisocyanate,
and/or their isocyanurate trimers, with
bis(3-propyltrimethoxysilyl)amine and at least one
hydroxyl-containing polysiloxane of the abovementioned formula
(III) as surface-active compound (OV).
[0199] The reaction of the polyisocyanates with the aminosilanes
takes place preferably in an inert gas atmosphere at temperatures
of not more than 100.degree. C., preferably of not more than
60.degree. C.
[0200] In the reaction of the di- and/or polyisocyanates with the
aminosilanes (VII), preferably at least 50 mol %, more preferably
at least 70 mol %, and not more than 98 mol %, in particular not
more than 99 mol %, of the isocyanate groups of the di- and/or
polyisocyanate (PI) have undergone reaction to form structural
units (VI). The remaining isocyanate groups are then reacted with
suitable surface-active compounds (OV). It is also possible,
however, first to react some of the di- and/or polyisocyanate with
suitable surface-active compounds (OV) and subsequently to perform
the reaction with the aminosilanes. Also possible, finally, is the
simultaneous reaction of all the compounds with one another (in
situ process).
[0201] The amounts of the di- and/or polyisocyanates and of the
aminosilanes (VII) and of the surface-active compound (OV) are
preferably selected such that component (D1) contains on average
less than 50 mol % of free isocyanate groups.
[0202] The surface-active compound (OV) is employed typically in an
amount of 0.05% to 50% by weight, preferably in an amount of 0.1%
to 10% by weight, based in each case on the amount of component
(D1) employed, without solvent.
[0203] Component (D1) is typically employed in amounts sufficient
to exert targeted control over the properties of the at least
partly crosslinked coating. The fraction of component (D1) as a
proportion of the coating composition of the invention is
preferably from 0.1% to 35% by weight, more preferably from 0.5% to
15% by weight, very preferably from 1% to 10% by weight, based in
each case on the nonvolatiles content of the coating
composition.
Crosslinkable Component (D2)
[0204] As crosslinkable component (D2) it is possible, for example,
to use all film-forming materials which are typically employed in
coating compositions. As a result of the addition of the specific
surface-active component (D1), these coating compositions are
modified in such a way that the surface properties of the resulting
coating can be set in the targeted way already described.
[0205] As component (D2) it is possible to use compounds which are
able to form nodes with the crosslinkable groups of the component
(D1) and/or with themselves, where appropriate under catalysis,
and/or with a crosslinking agent (VM).
[0206] When selecting the crosslinkable component (D2) it should
preferably be ensured that, when the coating compositions are
cured, hydrolysis-labile Si--N--C and/or Si--O--C nodes are formed
only to a very minor extent, or not at all.
[0207] As component (D2), therefore, it is possible to employ
oligo- and/or polyurethane (meth)acrylates, polyester
(meth)acrylates, epoxy (meth)acrylates, (meth)acryloyl-functional
(meth)acrylic copolymers, polyether (meth)acrylates, unsaturated
polyesters, amino (meth)acrylates, melamine (meth)acrylates and/or
silicone (meth)acrylates containing one or more double bonds,
preferably polyurethane (meth)acrylates and/or polyester
(meth)acrylates, which in addition to the double bonds may where
appropriate also have carbamate, biuret, allophanate, amide, urea,
hydroxyl, carboxyl and/or epoxide groups.
[0208] The urethane (meth)acrylates can be prepared in a manner
known to the skilled worker from di- and/or polyisocyanates, from
at least one compound containing groups that are reactive toward
isocyanate groups, and from at least one compound which contains
groups that are reactive toward isocyanate groups and also contains
at least one ethylenically unsaturated group, preparation taking
place by mixing of the components in any order, where appropriate
at an elevated temperature.
[0209] In particular the urethane (meth)acrylates are obtained by
initially introducing the di- or polyisocyanate and then adding at
least one hydroxyalkyl (meth)acrylate or hydroxyalkyl ester of
other ethylenically unsaturated carboxylic acids, as a result of
which some of the isocyanate groups are reacted to start with.
Subsequently a chain extender from the group of the diols/polyols
and/or diamines/polyamines and/or dithiols/polythiols and/or
alkanolamines is added, and in that way the remaining isocyanate
groups are reacted with the chain extender.
[0210] The polyester (meth)acrylates that are suitable in addition
to the urethane (meth)acrylates are known in principle to the
skilled worker. They can be prepared by a variety of methods. For
example, acrylic and/or methacrylic acid can be used directly as an
acid component when synthesizing the polyesters. Another
possibility is to use hydroxyalkyl esters of (meth)acrylic acid as
an alcohol component directly when synthesizing the polyesters.
Preferably, however, the polyester (meth)acrylates are prepared by
acrylation of polyesters. By way of example it is possible first to
synthesize hydroxyl-containing polyesters, which are then reacted
with acrylic or methacrylic acid. It is also possible first to
synthesize carboxyl-containing polyesters, which are then reacted
with a hydroxyalkyl ester of acrylic or methacrylic acid. Unreacted
(meth)acrylic acid can be removed from the reaction mixture by
washing, by distillation or, preferably, by reaction with an
equivalent amount of a monoepoxide or diepoxide compound, using
suitable catalysts, such as triphenylphosphine, for example. For
further details of the preparation of the polyester acrylates
reference may be made in particular to DE-A 33 16 593 and DE-A 38
36 370 and also to EP-A-54 105, DE-B 20 03 579, and EP-B-2866.
[0211] The polyether (meth)acrylates that are also suitable are
likewise known in principle to the skilled worker. They can be
prepared by a variety of methods. For example, hydroxyl-containing
polyethers which are esterified with acrylic acid and/or
methacrylic acid can be obtained by reacting dihydric and/or
polyhydric alcohols with different amounts of ethylene oxide and/or
propylene oxide in accordance with well-known methods (cf., e.g.,
Houben-Weyl, volume XIV, 2, Makromolekulare Stoffe [Macromolecular
compounds] II, (1963)). It is also possible to use polymerization
products of tetrahydrofuran or of butylene oxide.
[0212] Furthermore, epoxy (meth)acrylates as well are well known to
the skilled worker and therefore require no detailed elucidation.
They are typically prepared by addition reaction of acrylic acid
with epoxy resins, for example with epoxy resins based on bisphenol
A, or other commercially customary epoxy resins.
[0213] In particular the crosslinkable component (D2) is composed
of one or more binders (BM) and, where appropriate, of one or more
crosslinking agents (VM) as well.
[0214] The binders (BM) are preferably selected from the group of
oligomeric and/or polymeric compounds which contain
radiation-crosslinkable groups, more particularly ethylenically
unsaturated groups, such as acrylate and/or methacrylate groups,
and/or thermally crosslinkable groups, such as hydroxyl groups,
carbamate groups, epoxy groups, isocyanate groups, carboxyl and/or
anhydride groups, preferably hydroxyl groups and/or carbamate
groups and/or acrylate and/or methacrylate groups, and/or the
crosslinking agents (VM) are selected from the group consisting of
amino resins, nonblocked di- and/or polyisocyanates, blocked di-
and/or polyisocyanates, polyepoxides, polycarboxylic acids,
polyanhydrides, and polyols.
[0215] Use is made in particular of binders (BM) based on
polyurethanes and/or poly (meth)acrylates and/or polyesters which
contain thermally curable groups, more particularly hydroxyl and/or
carbamate groups.
[0216] The binders typically have number-average molecular weights,
determined by gel permeation chromatography against polystyrene
standards, of 500 to 20 000, more particularly of 500 to 4000.
[0217] The OH number of the OH-containing binders is preferably
between 50 and 500 mg KOH/g, more particularly between 70 and 250
mg KOH/g, determined in each case in accordance with DIN EN ISO
4629, 07.1998 edition.
[0218] Binders containing carbamate groups typically have an
arithmetic carbamate equivalent weight, CEW, of 250 to 700
g/equivalent, more particularly of 250 to 500 g/equivalent.
[0219] As binders (BM) use is made, for example, of (meth)acrylate
copolymers obtainable by copolymerizing [0220] (a1)) 10% to 80% by
weight, preferably 20% to 60% by weight, of 3-hydroxypropyl
acrylate or 3-hydroxypropyl methacrylate or 2-hydroxypropyl
acrylate or 2-hydroxypropyl methacrylate or 2-hydroxyethyl acrylate
or 2-hydroxyethyl methacrylate or 4-hydroxy-n-butyl acrylate or
4-hydroxy-n-butylmethacrylate or mixtures of these monomers, [0221]
(b1) 0% to 30% by weight, preferably 0% to 15% by weight, of a
non-(a1) hydroxyl-containing ester of acrylic acid or of a
hydroxyl-containing ester of methacrylic acid or of a mixture of
such monomers, [0222] (c1) 0% to 90% by weight, preferably 10% to
70% by weight, of a non-(a1) and non-(b1) aliphatic or
cycloaliphatic ester of (meth)acrylic acid having at least 4 carbon
atoms in the alcohol residue, or of a mixture of such monomers,
[0223] (d1) 0% to 3% by weight, preferably 0% to 2% by weight, of
an ethylenically unsaturated carboxylic acid or of a mixture of
ethylenically unsaturated carboxylic acids, and [0224] (e1) 0% to
50% by weight, preferably 0% to 35% by weight, of a vinyl-aromatic
compound and/or of a non-(a1), non-(b1), non-(c1), and non-(d1)
ethylenically unsaturated monomer or of a mixture of such monomers,
the sum of the weight fractions of components (a1), (b1), (c1),
(d1), and (e1) always making 100% by weight.
[0225] The crosslinking agents (VM) are selected in particular from
the group consisting of amino resins, nonblocked polyisocyanates,
blocked polyisocyanates, polyepoxides, polycarboxylic acids,
polyanhydrides, and polyols.
[0226] Suitable amino resins are the typical and known amino resins
some of whose methylol and/or methoxymethyl groups may have been
defunctionalized by means of carbamate or allophanate groups.
Crosslinking agents of this kind are described in patents U.S. Pat.
No. 4,710,542 and EP-B-0 245 700 and also in the article by B.
Singh and coworkers, "Carbamylmethylated Melamines, Novel
Crosslinkers for the Coatings Industry" in Advanced Organic
Coatings Science and Technology Series, 1991, volume 13, pages 193
to 207.
[0227] Other suitable crosslinking agents (VM) are epoxy resins,
which preferably react with themselves under the catalysis of
component (C), particular preference being given to aliphatic epoxy
resins which exhibit a high weathering stability. Epoxy resins of
this kind are described in, for example, the monograph by B. Ellis
"Chemistry and Technology of Epoxy Resins" (Blackie Academic &
Professional, 1993, pages 1 to 35).
[0228] As crosslinking agents (VM) it is preferred to use di-
and/or polyisocyanates. Examples of suitable di- and/or
polyisocyanates are the di- and/or polyisocyanates already
described above in connection with component (D1). Preference is
given to using aliphatic and/or cycloaliphatic di- and/or
polyisocyanates.
[0229] When the isocyanates are used in 1K (one-component) coating
materials, the isocyanates are reacted, in a manner known to the
skilled worker, with a blocking agent, the selection of the
blocking agent being guided in particular by the desired curing
temperature, as the skilled worker is aware.
[0230] Generally speaking, component (D2) is employed in fractions
of 50% to 99.8% by weight, preferably of 80% to 99.4% by weight,
more preferably of 85% to 98.5% by weight, based on the
nonvolatiles of the coating composition.
[0231] The binders (BM) are employed typically in fractions of 1%
to 70%, preferably of 10% to 50%, more preferably of 20% up to 45%
by weight, based on the nonvolatiles of the coating
composition.
[0232] The crosslinking agents (VM) are employed typically in
fractions of 1% to 70%, preferably of 10% to 60%, more preferably
of 25% up to 55% by weight, based on the nonvolatiles of the
coating composition.
Further Constituents of the Coating Composition (B)
[0233] The coating compositions (B) preferably further comprise one
or more catalysts (C) for the crosslinking of the reactive groups
of component (D1), more particularly for the crosslinking of the
silane groups.
[0234] As catalysts (C) for the crosslinking of the silane groups
or of the alkoxysilane groups it is possible in principle to employ
compounds which are known per se. Examples are Lewis acids
(electron deficiency compounds), such as tin naphthenate, tin
benzoate, tin octoate, tin butyrate, dibutyltin dilaurate,
dibutyltin diacetate, dibutyltin oxide, and lead octoate, for
example. There are concerns about the toxicity of these compounds,
though. In particular, when effective amounts for silane
crosslinking are to be used, catalysts of this kind display a
tendency toward yellowing, particularly on overbaking, i.e., on
crosslinking at a relatively high temperature, at 160.degree. C.,
for example. Stability to such overbaking, however, is a
prerequisite for the use of OEM clearcoats in line production.
Other, less toxicologically objectionable catalysts are metal
complexes with chelate ligands, based on aluminum or else on zinc,
examples being the catalysts described in WO-A-2006/042585, page 10
lines 4 to 21. These catalysts also display a tendency toward
severe yellowing on overbake, and ought therefore as far as
possible not to be used in the formulations of the invention.
[0235] As far as the toxicological properties and yellowing in
overbake tests are concerned, the invention prefers catalysts based
on derivatives of phosphorus acids.
[0236] As catalyst (C) use is therefore made in particular of
substituted phosphonic diesters and diphosphonic diesters,
preferably from the group consisting of acyclic phosphonic
diesters, cyclic phosphonic diesters, acyclic diphosphonic
diesters, and cyclic disphosphonic diesters, and also substituted
phosphoric monoesters and phosphoric diesters, preferably from the
group consisting of acyclic phosphoric diesters and cyclic
phosphoric diesters, or the corresponding amine-blocked esters.
Suitable phosphorus catalysts are described in, for example, the as
yet unpublished German patent application DE
P102005045228.0-44.
[0237] As catalyst (C) it is preferred to employ correspondingly
substituted phosphoric monoesters and phosphoric diesters,
preferably from the group consisting of acyclic phosphoric diesters
and cyclic phosphoric diesters.
[0238] The acyclic phosphonic diesters (C) here are selected in
particular from the group consisting of acyclic phosphonic diesters
(C) of the general formula (VIII):
R.sup.10--O
P(O)H;
R.sup.11--O (VIII)
where the radicals R.sup.10 and R.sup.11 are alike or different
from one another; preferably they are alike.
[0239] The radicals R.sup.10 and R.sup.11 are selected from the
group consisting of: [0240] substituted and unsubstituted alkyl
having 1 to 20, preferably 2 to 16, and more particularly 2 to 10
carbon atoms, cycloalkyl having 3 to 20, preferably 3 to 16 and
more particularly 3 to 10 carbon atoms, and aryl having 5 to 20,
preferably 6 to 14, and more particularly 6 to 10 carbon atoms,
[0241] substituted and unsubstituted alkylaryl, arylalkyl,
alkylcycloalkyl, cycloalkylalkyl, arylcycloalkyl, cycloalkylaryl,
alkylcycloalkylaryl, alkylarylcycloalkyl, arylcycloalkylalkyl,
arylalkylcycloalkyl, cycloalkylalkylaryl, and cycloalkylarylalkyl,
the alkyl, cycloalkyl, and aryl groups they contain each containing
the aforementioned number of carbon atoms, and [0242] substituted
and unsubstituted radical of the aforementioned kind containing at
least one, more particularly one, heteroatom selected from the
group consisting of oxygen atom, sulfur atom, nitrogen atom,
phosphorus atom, and silicon atom, more particularly oxygen atom,
sulfur atom, and nitrogen atom.
[0243] Preference is given to using the acyclic phosphonic diesters
(C) of the general formula (VIII), more particularly those in which
the radicals R.sup.10 and R.sup.11 of the general formula (VIII)
are selected from the group consisting of phenyl, methyl, and
ethyl. One example of a highly suitable phosphonic diester (C) of
the general formula (VIII) is diphenyl phosphonate, which is
sometimes also referred to by those in the art (not entirely
correctly) as diphenyl phosphite.
[0244] Employed with particular preference as catalyst (C) are
correspondingly substituted phosphoric monoesters and phosphoric
diesters, preferably from the group consisting of acyclic
phosphoric diesters and cyclic phosphoric diesters.
[0245] These acyclic phosphoric monoesters and diesters (C) are
selected more particularly from the group consisting of acyclic
phosphoric monoesters and diesters (C) of the general formula
(IX):
R.sup.10--O
P(O)OH;
R.sup.11--O (IX)
where R.sup.10 and R.sup.11 are as defined above and in addition
may also represent hydrogen (partial esterification).
[0246] Examples of especially suitable phosphoric esters (C) are
the corresponding amine-blocked phosphoric esters, more
particularly amine-blocked ethylhexyl phosphate and amine-blocked
phenyl phosphate.
[0247] As far as the amine is concerned that is used to block the
phosphoric esters, particular preference is given to triethylamine.
Certain amine-blocked phosphoric acid catalysts are also available
commerically. As an example, mention may be made of the substance
sold under the designation Nacure 4167 by King Industries as a
particularly suitable catalyst based on an amine-blocked partial
ester of phosphoric acid.
[0248] Catalyst (C) is typically employed in fractions of 0.1% to
15% by weight, preferably of 0.5% to 5% by weight, based on the
nonvolatiles of the coating composition.
[0249] The coating compositions further typically comprise solvents
(L). Particularly suitable solvents are aprotic solvents which
within the coating composition are chemically inert toward the
other components and which also do not react when the coating
composition is cured. Examples of this kind of solvent are
aliphatic and/or aromatic hydrocarbons such as toluene, xylene,
Solventnaphtha.RTM., Solvesso 100 or Hydrosol.RTM. (ARAL), ketones,
such as acetone, methyl ethyl ketone or methyl amyl ketone, esters,
such as ethyl acetate, butyl acetate, pentyl acetate or ethyl
ethoxypropionate, ethers, or mixtures of the aforementioned
solvents. The aprotic solvents or solvent mixtures preferably have
a water content of not more than 1% by weight, more preferably not
more than 0.5% by weight, based on the solvent.
[0250] The coating compositions of the invention may further
comprise typical auxiliaries and additives, such as catalysts for
crosslinking components (D1) and (D2), defoamers, adhesion
promoters, additives for enhancing substrate wetting, additives for
enhancing surface smoothness, matting agents, light stabilizers,
preferably UV absorbers and/or HALS, corrosion inhibitors,
biocides, flame retardants or polymerization inhibitors, for
example, as described in detail in the book "Lackadditive"
[Additives for Coatings] by Johan Bieleman, Wiley-VCH, Weinheim,
N.Y., 1998, in typical amounts, more particularly in amounts of up
to 5% by weight, based on the total weight of the coating
composition.
[0251] Particularly preferred coating compositions are obtained
when the amount of other, noncrosslinking surface-active
substances, i.e., of surface-active substances with the exception
of component (D1), is kept as low as possible. More particularly
the amount of these other, noncrosslinking surface-active
substances is below 0.5% by weight and more preferably below 0.1%
by weight, based in each case on the total weight of the coating
composition. Examples of such other, noncrosslinking surface-active
substances are, in particular, typical flow control additives and
the like.
Multicoat Effect and/or Color Paint Systems
[0252] The coating compositions of the invention are outstandingly
suitable as decorative, protective and/or effect-imparting, highly
scratchproof coatings and paint systems, more particularly as the
transparent coating of a multicoat effect and/or color paint
system, on bodies of means of transport or parts thereof (more
particularly motor vehicles, such as motorcycles, buses or
automobiles, commercial vehicles, such as agricultural machinery
and trucks, and also in aircraft construction and shipbuilding, and
for interior and exterior bodywork components) in the OEM and
refinish segments; on buildings, both interior and exterior; on
furniture, windows, and doors; on plastics moldings, more
particularly CDs and window; on small industrial parts, on coils,
containers, and packaging; on white goods; on films; on optical,
electrical, and mechanical components; and on hollow glassware and
articles of everyday use.
[0253] The coating compositions and paint systems of the invention,
more particularly the clearcoats, are employed in particular in the
technologically and esthetically particularly demanding field of
automotive OEM finishing. With particular preference the coating
compositions of the invention are used in multistage coating
methods, particularly in methods where at least one pigmented
coating composition is applied to a precoated or unprecoated
substrate and thereafter a transparent coating composition is
applied to at least part of the resulting pigmented coating, and
cured, the transparent coating being produced from the coating
compositions of the invention.
[0254] This method is employed in particular in automotive OEM
finishing and/or commercial vehicle finishing and/or refinish, for
the coating of interior or exterior bodywork components or of
components for shipbuilding or aircraft construction, or of
components for household and electrical appliances, or of plastics
moldings or films.
[0255] Preference is also given, accordingly, to multicoat paint
systems composed of at least one pigmented coating and, atop it, a
transparent coating, the transparent coating having been produced
from the coating composition of the invention.
[0256] The pigmented coatings employed in this case may have been
produced using either aqueous or solventborne pigmented coating
compositions, which in general are curable physically or thermally
and/or with actinic radiation.
[0257] The pigmented coating compositions typically comprise [0258]
(I) one or more solvents and/or water, [0259] (II) one or more
binders, preferably one or more polyurethane resins and/or acrylate
resins and/or polyester resins, more preferably at least one
polyurethane resin, [0260] (III) if desired, at least one
crosslinking agent, [0261] (IV) one or more pigments, especially
effect pigments and/or color pigments, and [0262] (V) if desired,
one or more typical auxiliaries and additives.
[0263] Suitable binders here are the polyurethane resins, acrylate
resins, and polyester resins that are typically employed in
basecoats in the automotive industry segment, the properties and
hence the suitability of the binders for the method of the
invention being directed, in a manner known to the skilled worker,
via the selection of the nature and amount of the synthesis
components used for preparing these binders.
[0264] Preference is given to using polyurethane resins, where
appropriate in combination with one or more polyacrylate resins
and/or with one or more polyester resins.
[0265] Suitable pigmented coating compositions (basecoat materials)
are described in, for example, EP-A-0 692 007 and in the documents
it cites at column 3 lines 50 et seq.
[0266] The coating compositions of the invention can be applied by
any customary application method, such as spraying, knifecoating,
spreading, pouring, dipping, impregnating, trickling or rolling,
for example. The substrate to be coated may itself be at rest, with
the application equipment or unit being moved. Alternatively the
substrate to be coated, more particularly a coil, may be moved,
with the application unit being stationary relative to the
substrate or being moved in an appropriate way. Preference is given
to employing spray application methods, such as compressed-air
spraying, airless spraying, high-speed rotation or electrostatic
spray application (ESTA), for example, where appropriate in
conjunction with hot spray application such as hot-air spraying,
for example.
[0267] Curing of the applied coating compositions of the invention
may take place after a certain rest time. This rest time serves,
for example, for the leveling and degassing of the coating films or
for the evaporation of volatile constituents such as solvents. The
rest time may be shortened and/or assisted through the application
of elevated temperatures and/or through a reduced humidity,
provided this is not accompanied by any damage to or change in the
coating films, such as premature complete crosslinking, for
instance.
[0268] In the case of radiation-curable film-forming materials,
curing takes place, in a manner known to the skilled worker, by
means of radiation, more particularly by means of UV radiation. It
is preferred to use a radiation dose of 100 to 6000, preferably 200
to 3000, more preferably 300 to 2500, and with particular
preference 500 to 2000 mJ cm.sup.-2. Irradiation may be carried out
under an oxygen-depleted atmosphere. "Oxygen-depleted" means that
the oxygen content of the atmosphere is lower than the oxygen
content of air (20.95% by volume). In principle the atmosphere may
also be oxygen-free, i.e., it may comprise an inert gas. On account
of the absence of the inhibiting effect of oxygen, however, this
may result in a sharp acceleration to the radiation cure, possibly
leading to inhomogeneities and stresses. It is therefore
advantageous not to lower the oxygen content of the atmosphere to
zero % by volume.
[0269] There are no peculiarities in terms of method to the thermal
curing of the coating compositions, which instead takes place in
accordance with the typical, known methods, such as heating in a
forced-air oven or irradiation using IR lamps. This thermal curing
may also take place in stages. Another preferred curing method is
that of curing with near infrared (NIR) radiation. The thermal
curing takes place advantageously at a temperature of 50 to
200.degree. C., more preferably 60 to 190.degree. C., and in
particular 80 to 180.degree. C., for a time of 1 min up to 5 h,
more preferably 2 min up to 2 h, and in particular 3 min to 90
min.
[0270] The coating compositions of the invention yield new cured
coatings, especially surface coatings, more particularly
clearcoats, moldings, more particularly optical moldings, and
self-supporting films, all of which are highly scratchproof and in
particular are stable to chemicals and to weathering. In particular
the coatings and surface coatings of the invention, more
particularly the clearcoats, can be produced even in film
thicknesses >40 .mu.m without the occurrence of stress
cracks.
Method of Controlling the Properties of a Coating
[0271] Also provided in accordance with the invention, furthermore,
is a method of controlling the properties of at least partly
crosslinked coatings (K),
[0272] wherein the coating (K) is composed of a near-surface
coating zone (K1) and a volume coating zone (K2), and the coating
(K) is produced from a coating composition which comprises at least
two different crosslinkable components (D1) and (D2), at least part
of component (D1) having one or more surface-active structural
units (O); wherein [0273] (i) the crosslinking density of the
network (N1) formed from component (D1) is higher than the
crosslinking density of the network (N2) formed from component
(D2), and [0274] (ii) the properties of the coating are controlled
by way of the ratio of the crosslinking density of the network (N1)
formed from component (D1) to the crosslinking density of the
network (N2) formed from component (D2).
[0275] As already observed above, the near-surface coating zone
(K1) is formed substantially by the at least partly crosslinked
component (D1) and the volume coating zone (K2) is formed
substantially by the at least partly crosslinked component
(D2).
Determining the Properties of the Coating (K)
[0276] The cured coatings of the invention, especially surface
coatings, more particularly clearcoats, are highly scratch proof
and in particular are stable to chemicals and to weathering. In
particular it is possible to produce the coatings and surface
coatings of the invention, more particularly the clearcoats, even
in film thicknesses >40 .mu.m, without stress cracks
occurring.
[0277] Thus the cured coatings of the invention, and preferably the
corresponding transparent coatings of a multicoat color and/or
effect paint system, are notable for very good micropenetration
hardness. These cured coatings preferably have a micropenetration
hardness of at least 90 N/mm.sup.2, more particularly of at least
100 N/mm.sup.2, and with very particular preference of at least 110
N/mm.sup.2. This micropenetration hardness is measured on coatings
which have a dry film thickness of 40 .mu.m and which have been
dried at 140.degree. C. for 22 minutes and stored at 25.degree. C.
for 5 days before the micropenetration hardness is measured. The
micropenetration hardness was determined in accordance with DIN EN
ISO 14577 with the aid of the Fischerscope instrument from Fischer,
with a maximum force of 25.6 mN.
[0278] The cured coatings of the invention are notable in
particular for improved dry scratch resistance. The dry scratch
resistance was determined using the crockmeter test (9 .mu.m paper
grade). This was done by operating along the lines of EN ISO 105-X
12 and evaluating the loss of gloss at 20.degree. after 10 double
rubs. The coating compositions of the invention are also suitable
for scratchproofing exposed areas on painted automobile bodies.
[0279] The chemical surface properties, and especially the gradient
of the chemical disuniformity, are determined via photoelectron
spectroscopy (XPS), the information depth, for detection of the
gradient, being varied via exit angle variation or sputter depth
profile analysis, and with the aid of transmission electron
microscopy together with EDX (energy dispersive X-ray
spectroscopy).
[0280] All the XPS measurements were carried out on a small-spot
spectrometer from Physical Electronics, with the model
identification PHI 5600 LS. The X-rays were always generated using
the Mg tube (1253.6 keV). The detection of the photoelectrons, with
a pass energy of 23.5 eV, used the following bond levels to
determine the atomic concentrations: for Si, the 2p level, for O,
the 1s level, and for C as well the 1s level. By varying the angle
of detection of the photoelectrons--that is, the angle between the
sample surface and the axis of the electronic lenses in front of
the electron spectrometer--the depth at which the measurement
signals are generated (information depth) was changed: at 5.degree.
the information depth is about 1.2 nm (XPS(Si) 1.2 nm), at
45.degree. about 10 nm (XPS(Si) 10 nm). At the detection angle of
45.degree. the measurement area has a diameter of 800 .mu.m; at
5.degree. it has undergone corresponding elliptic enlargement.
Following preparation of thin sections with a microtome, parallel
to the surface and approximately 10 .mu.m below the surface, a
reference value can be obtained at a comparative depth in material
(XPS(Si) 10 .mu.m).
[0281] The following nomenclature is used additionally to
characterize the results of the photoelectron spectroscopy:
[0282] XPS(Si) 1.2 nm stands for the fraction of the detected atoms
(in this case silicon) measured from an information depth of 1.2 nm
from the surface of the coating material. The totality of the
atomic species detectable by XPS at the stated information depth is
reported as 100%. As the skilled worker is aware, hydrogen, for
example, cannot be detected by XPS.
[0283] The thin sections were prepared starting from steel panels
with a corresponding complete system. The microtome sections were
prepared using a motorized commercial rotary microtome of type RM
2155, available from Leica Mikrosysteme, Bensheim. Prior to
sectioning, the desired thickness was first set. Subsequently the
respective metal panels were fixed. In the actual operational step,
the rotary microtome was run over the respective metal panels. The
resulting thin sections were employed for the further
investigations.
[0284] The physicomechanical properties can also be determined with
local and depth resolution by means of nanoindentation, using for
example the TriboIndenter.RTM. nanoindentation instrument from
Hysitron Inc. The experimental implementation of this test takes
place as follows: the impression body used is a three-sided diamond
pyramid in Berkovich geometry (opening angle 142.3.degree.) with an
extremely pointed tip (radius <100 nm). This body is then
pressed for 10 s into the surface of the coating, with a force
increasing linearly up to a maximum of 5 mN, the penetration depth
being between 1 .mu.m and 1.5 .mu.m, is held there for a further 30
s under maximum force, and over the next 10 s is withdrawn from the
surface with a linearly falling force. From the resulting dataset
of force versus depth of penetration, the known algorithm of Oliver
and Pharr (cf. W. C. Oliver, G. M. Pharr, Journal of Materials
Research. 7 (1992), 1565, G. M. Pharr, Materials Science and
Engineering A 253 (1998), 151) is used to determine the mechanical
data of the analyzed material with local resolution.
EXAMPLES
1.1. Preparation of an Adduct (AV1)
[0285] A reaction vessel equipped with stirrer, reflux condenser,
oil heating, and nitrogen inlet tube was charged with 456.38 parts
by weight of a commercial isocyanurate of hexamethylene
diisocyanate (Desmodur N 3600 from Bayer AG). Added slowly to this
initial solution of the isocyanurate, with stirring, were 815.62
parts by weight of N,N-bis(3-trimethoxysilylpropan-1-yl)amine
(Dynasylan.RTM. 1124 from Degussa). This was followed by stirring
at 55.degree. C. for a further two hours. Thereafter free
isocyanate groups were no longer detectable by IR spectroscopy. The
resulting compound (AV1) had a solids content of 79%.
1.2. Preparation of a Surface-Modified Adduct (A1)
[0286] A reaction vessel equipped with stirrer, reflux condenser,
oil heating, and nitrogen inlet tube was charged with 100 parts by
weight of a commercial isocyanurate of hexamethylene diisocyanate
(Desmodur N 3600 from Bayer AG). Added slowly to this initial
solution of the isocyanurate, with stirring, was a solution of 15
parts by weight of a carbinol-functional siloxane (Baysilone.RTM.
OF 502 6% from GE-Bayer Silicones) in 3.75 parts by weight of the
commercial aromatic solvent Solventnaphta.RTM.. Following the
addition, the reaction mixture was heated to 55.degree. C. and
stirred at 55.degree. C. for a further 2 hours. Next, slowly and
with stirring, 172.5 parts by weight of
N,N-bis(3-trimethoxysilylpropan-1-yl)amine (Dynasylan.RTM. 1124
from Degussa) were added to the mixture. Stirring was then carried
out at 55.degree. C. for a further two hours. Thereafter free
isocyanate groups were no longer detectable by IR spectroscopy. The
resulting compound (A1) had a solids content of 80.8%. The surface
tension of the reactants employed and of the adduct A1 was
determined by means of the ring method. The results obtained are
compiled in the table below:
TABLE-US-00001 Substance Surface tension .sigma./[mN/m]
N,N-Bis(3-trimethoxysilylpropan-1- 30.3 yl)amine (Dynasylan .RTM.
1124) Baysilone .RTM. OF 502 6% (GE Bayer 21.7 Silicones) Desmodur
N 3600 (Bayer AG) 43.2 Adduct A1 26.5
1.3. Preparation of a Catalyst (C1) Based on an Amine-Blocked
Phosphoric Ester
[0287] A reactor equipped with a dropping funnel and a reflux
condenser was charged with 43.2 parts by weight of phenyl phosphate
and 39.2 parts by weight of methoxypropyl acetate and this initial
charge was homogenized. Subsequently, with cooling and stirring,
17.6 parts by weight of triethylamine were added dropwise at a rate
such that the temperature did not exceed 60.degree. C. Following
addition of the triethylamine, the reaction mixture was stirred at
room temperature for 2 hours more. The resulting reaction product
had a solids content of 50.0%.
1.4. Preparation of a Hydroxyl-Containing Polyacrylate (PAC 1)
[0288] A reactor flushed with nitrogen and with a condenser
attached was charged with 30.4 parts by weight of
Solventnaphta.RTM., and this initial charge was heated to
140.degree. C. with stirring. In parallel with this, two separate
feed streams were prepared. Feed stream 1 consisted of 13.9 parts
by weight of styrene, 26.7 parts by weight of butyl acrylate, 15.0
parts by weight of hydroxyethyl acrylate, and 1.4 parts by weight
of acrylic acid. Feed stream 2 consisted of 5.9 parts by weight of
Solventnaphta.RTM. and 1.30 parts by weight of peroxide DTBP
(=di-tert-butyl peroxide). When the temperature of 140.degree. C.
had been reached, feed stream 2 was metered in slowly and uniformly
over a period of 285 minutes. 15 minutes after the start of feed
stream 2, feed stream 1 was metered slowly and uniformly into the
reactor over a period of 240 minutes. After the end of the metering
of feed stream 2, the reaction mixture was stirred at 140.degree.
C. for a further 120 minutes for postpolymerization. The solids
content of the resulting product was found to be 60%, the acid
number 19 mg KOH/g and the OH number 128 mg KOH/g (in each case
based on the solids) and the viscosity 9.5 dPas at 23.degree.
C.
1.5. Preparation of an Acrylate-Based Rheological Assistant
[0289] A methacrylate copolymer is prepared in 32.02 parts by
weight of Solventnaphta.RTM. from 25.67 parts by weight of styrene,
22.30 parts by weight of n-butyl acrylate, 13.87 parts by weight of
2-hydroxyethyl acrylate, 1.41 parts by weight of ethacrylic acid,
and 0.870 part by weight of lauryl methacrylate (MA-13, available
from Degussa).
[0290] 84.7 parts by weight of the resulting methacrylate
copolymer, 5.88 parts by weight of butyl acetate, 2.24 parts by
weight of benzylamine, and 1.76 parts by weight of hexamethylene
diisocyanate, in solution in 3.42 parts by weight of butyl acetate,
are used to prepare a urea-modified, acrylate-based rheological
assistant which had a solids of 59%.
2. Preparation of the 1-Component (1K) Clearcoat Materials 1 to
6
[0291] The raw materials set out in Table 1 were combined in
succession in the quantities indicated, and homogenized, in order
to prepare the 1K clearcoat materials.
TABLE-US-00002 TABLE 1 Composition of the 1K clearcoat materials of
comparative examples C1, C2, C3, and C4, and also of inventive
examples 1 and 2 Ingredient [parts by Example Example Example
Example Example Example weight] C1 1 C2 C3 2 C4 Acrylate resin 25.8
25.8 25.8 25.8 25.8 25.8 PAC1 from 1.4. Luwipal 018 BX .sup.1) 25.3
25.3 25.3 25.3 25.3 25.3 Adduct (A1) 0 5.0 0 0 5.0 0 from 1.2.
Addukt (AV1) 0 0 5.00 0 0 5.00 from 1.1. Desmodur PL 7.6 0 0 7.6 0
0 350 .sup.2) Rheological 21 21 21 21 21 21 assistant from 1.5.
Solvent 0 1.9 1.9 0 1.9 1.9 mixture.sup.3) Xylene 1.185 1.185 1.185
1.185 1.185 1.185 Solventnaphta .RTM. 7.9 7.9 7.9 7.9 7.9 7.9 Byk
310 .sup.4) 0 0 0 0.1 0.1 0.1 Baysilon OL 17 .sup.5) 0 0 0 0.015
0.015 0.015 Tinuvin 5941-R .sup.6) 0.85 0.85 0.85 0.85 0.85 0.85
Tinuvin 292 .sup.7) 0.05 0.05 0.05 0.05 0.05 0.05 Solvesso 150
.sup.8) 6.7 6.7 6.7 6.7 6.7 6.7 Butylglycol 1 1 1 1 1 1 diacetate
Catalyst (C1) 0 1 1 0 1 1 from 1.3. Nacure 4167 .sup.9) 0.5 0.5 0.5
0.5 0.5 0.5 Butanol 2 2 2 2 2 2 Flow control 0.7 0.7 0.7 0.7 0.7
0.7 agent.sup.10) Footnotes to Table 1: .sup.1) Luwipal 018 BX =
commercial, partially butanol-etherified melamine-formaldehyde
resin from BASF AG, 64-68% in 2:1 n-butanol/xylene .sup.2) Desmodur
PL 350 = commercial aliphatic blocked isocyanate from Bayer, 75% in
11/14 1-methoxyprop-2-ylacetate/Solventnaphta .RTM. .sup.3)Solvent
mixture consisting of 1-methoxyprop-2-ylacetate and Solventnaphta
.RTM. in a ratio of 11:14 .sup.4) Byk .RTM. 310 = commercial flow
control additive based on a 25% strength solution in xylene of a
polyester-modified polydimethylsiloxane, from Byk-Chemie GmbH,
Wesel .sup.5) Baysilon OL 17 = commercial flow control additive
from Borchers GmbH .sup.6) Tinuvin .RTM. 5941-R = commercial
mixture of different light stabilizers from Ciba Specialty
Chemicals Inc. .sup.7) Tinuvin .RTM. 292 = commercial light
stabilizer based on sterically hindered amines (HALS) from Ciba
Specialty Chemicals Inc. .sup.8) Solvesso 150 = commercial solvent
mixture .sup.9) Nacure 4167 = commercial catalyst from King
Industries based on an amine-blocked partial ester of phosphoric
acid .sup.10)Acrylate-based flow control agent with a solids
content of 65%, an acid number of 3 mg KOH/g (based on the solids),
and of a viscosity at 23.degree. C. of 3 dPa.cndot.s
3. Production of the Coatings
[0292] The individual 1K clearcoat materials as per Table 1 were
applied to metal test panels which had each been coated with a
typical, known, cathodically deposited and thermally cured
electrocoat, a typical, known, thermally cured surfacer coat, and a
film of a commercial, conventional black basecoat material from
BASF Coatings AG that had been subjected to initial drying at
80.degree. C. for 10 minutes. The basecoat film and the clearcoat
film were cured together at 140.degree. C. for 22 minutes. The
resulting basecoat had a film thickness of 7.5 .mu.m, and the
clearcoat a film thickness of 40 .mu.m.
4. Investigation of the Properties of the Resulting Coatings
[0293] All of the surfaces were of high gloss and outstanding
appearance. The dry scratch resistance of the resulting surfaces
was determined by means of the crockmeter test (9 .mu.m paper
grade). This was done by operating along the lines of EN ISO 105-X
12 and evaluating the loss of gloss at 20.degree. C. after 10
double rubs. Furthermore, the Konig pendulum damping was
investigated using the 299/300 model from Erichsen GmbH & Co.
KG, Hemer-Sundwig. The figure reported is the number of swings. The
micropenetration hardness was determined in accordance with DIN
55676 using the Fischerscope instrument from Helmut Fischer GmbH
& Co., with a maximum force of 25.6 mN. The results are set out
in Table 2.
TABLE-US-00003 TABLE 2 Results of the crockmeter test,
micropenetration hardness, and Konig pendulum damping (number of
swings) Clear- Clear- Clear- Clear- Clear- coat of coat of coat of
Clear- coat of coat of Ex- Ex- Ex- coat of Ex- Example ample ample
ample Example ample Test C1 1 C2 C3 2 C4 Micropenetration 98 125
121 112 120 117 hardness [N/mm.sup.2] Konig pendulum 58 67 61 59 70
64 damping Residual gloss 23% 90% 47% 59% 87% 68% after crockmeter
test [%]
[0294] The results show that the dry scratch resistance in
particular is increased significantly as a result of adding the
surface-modified adduct (A1) together with the catalyst (C)
(Example 1). If the non-surface-modified adduct (AV1) is used
(Example C2) in contrast, the improvement in particular in the dry
scratch resistance is significantly less pronounced. Example C3
shows that other surface-active substances as well, such as
commercial flow control agents, for example, do lead to an
improvement in the properties, but one which is substantially less
pronounced than when the surface-modified adduct (A1) is added.
Only if the adduct (A) has surface-active structures (O) is it
possible for a gradient structure with a dense, highly
scratch-resistant Si--O--Si network to form at the surface, this
network developing the outstanding properties on the surface. A
gradient structure of this kind can be detected, for example, by
means of X-ray photoelectron spectroscopy and with the aid of
transmission electron microscopy together with EDX
(energy-dispersive X-ray spectroscopy).
[0295] The physicomechanical properties can also be determined with
local and depth resolution by means of nanoindentation, using for
example the TriboIndenter.RTM. nanoindentation instrument from
Hysitron Inc. The experimental implementation of this test takes
place as follows: the impression body used is a three-sided diamond
pyramid in Berkovich geometry (opening angle 142.3.degree.) with an
extremely pointed tip (radius <100 nm). This body is then
pressed for 10 s into the surface of the coating, with a force
increasing linearly up to a maximum of 5 mN, the penetration depth
being between 1 .mu.m and 1.5 .mu.m, is held there for a further 30
s under maximum force, and over the next 10 s is withdrawn from the
surface with a linearly falling force. From the resulting dataset
of force versus depth of penetration, the known algorithm of Oliver
and Pharr (cf. W. C. Oliver, G. M. Pharr, Journal of Materials
Research. 7 (1992), 1565, G. M. Pharr, Materials Science and
Engineering A 253 (1998), 151) is used to determine the mechanical
data of the analyzed material with local resolution.
[0296] To illustrate the influence of the catalyst (C), the
clearcoat materials of Example 1 (=Comparative Example C5) and of
Comparative Example C2 (=Comparative Example 6) were repeated with
omission of the catalyst (C1) and, in the same way as for Examples
1 and C2, coatings C5 and C6 were produced and their
micropenetration hardness and dry scratch resistance in the
crockmeter test were measured. The results are set out in Table 3.
They show that the micropenetration hardness and the scratch
resistance of the coatings without catalyst (C) come out much lower
than in the corresponding examples with catalyst.
TABLE-US-00004 TABLE 3 Results of Comparative Examples C5 and C6
Clearcoat of Clearcoat of Clearcoat of Clearcoat of Test Example 1
Example C5 Example C2 Example 6 Micropene- 125 98 121 100 tration
hardness [N/mm.sup.2] Residual 90% 73% 47% 30% gloss after
crockmeter test [%]
[0297] In addition, the coatings of Examples 1 and 2 and of
Comparative Examples C1 to C4 were investigated using ARXPS
(=angle-dependent photoelectron spectroscopy). The results are set
out in Table 4. The information depth, for detecting the gradient,
was varied via exit angle variation or sputter depth profile
analysis.
[0298] All the XPS measurements were carried out on a small-spot
spectrometer from Physical Electronics, with the model
identification PHI 5600 LS. The X-rays were always generated using
the Mg tube (1253.6 keV). The detection of the photoelectrons, with
a pass energy of 23.5 eV, used the following bond levels to
determine the atomic concentrations: for Si, the 2p level, for O,
the 1s level, and for C as well the 1s level. By varying the angle
of detection of the photoelectrons--that is, the angle between the
sample surface and the axis of the electronic lenses in front of
the electron spectrometer--the depth at which the measurement
signals are generated (information depth) was changed: at 5.degree.
the information depth is about 1.2 nm (XPS(Si) 1.2 nm), at
45.degree. about 10 nm (XPS(Si) 10 nm). At the detection angle of
45.degree. the measurement area has a diameter of 800 .mu.m; at
5.degree. it has undergone corresponding elliptic enlargement.
Following preparation of sections with a microtome, parallel to the
surface and approximately 10 .mu.m below the surface, a reference
value can be obtained at a comparative depth in material (XPS(Si)
10 .mu.m).
TABLE-US-00005 TABLE 4 Results of ARXPS (=angle-dependent
photoelectron spectroscopy) measurements Clearcoat Clearcoat
Clearcoat Clearcoat Clearcoat Clearcoat of of of of of of
Measurement Example Example Example Example Example Example value
Cl 1 C2 C3 2 C4 Si (XPS, 1.3% 11.8% 1.6% 12.0% 15.2% 12.3% 1.2 nm)
Si (XPS, 10 nm) 0.4% 5.7% 1.5% 5.5% 8.2% 5.6% Si (XPS) 10 .mu.m
<0.2% 1.4% 1.5% 0.1% 0.9% 0.5% O (XPS, 1.2 nm) 13% 19.5% 17.4%
20.9% 22.1% 21.3% X.sub.surf - X.sub.vol 1.2% 10.0% <0.1% 11.9%
14.3% 11.8% XPS(Si 1.2 nm)/ 6.5 8.4 1 120 16.9 24.6 XPS(Si 10
.mu.m) XPS(Si)/ 0.1 0.6 0.09 0.57 0.69 0.58 XPS(O) XPS(Si 1.2 nm)/
3.25 2.07 1.07 2.18 1.85 2.20 XPS(Si 10 nm) tau 0.007 .mu.m 0.01
.mu.m no 0.01 .mu.m 0.01 .mu.m 0.01 .mu.m gradient
[0299] The following nomenclature is used additionally to
characterize the results of the photoelectron spectroscopy:
[0300] XPS(Si) 1.2 nm stands for the fraction of the detected atoms
(in this case silicon) measured from an information depth of 1.2 nm
from the surface of the coating material. The totality of the
atomic species detectable by XPS at the stated information depth is
reported as 100%. As the skilled worker is aware, hydrogen, for
example, cannot be detected by XPS.
[0301] Lastly, the coatings of Example 1 and of Comparative
Examples C2 and C3 were investigated by transmission electron
microscopy together with EDX (energy-dispersive x-ray
spectroscopy). The results are shown in FIG. 2. FIG. 2 gives the
Si/C atomic ratios for the coatings of Example 1 and of the
Comparative Examples C2 and C3. FIG. 2 illustrates the accumulation
of the surface-modified adduct (A1), while the non-surface-modified
adduct (AV1) shows only very little accumulation in the
near-surface zone.
5.1. Preparation of a Surface-Modified Adduct (A2)
[0302] A reaction vessel equipped with stirrer, reflux condenser,
oil heating, and nitrogen inlet tube was charged with 100 parts by
weight of a commercial isocyanurate of hexamethylene diisocyanate
(Desmodur.RTM. N 3600 from Bayer AG). Added slowly to this initial
solution of the isocyanurate, with stirring, was a solution of 2.5
parts by weight of a carbinol-functional siloxane (Baysilone.RTM.
OF 502 6% from GE-Bayer Silicones) in 0.625 part by weight of the
commercial aromatic solvent Solventnaphta.RTM.. Following the
addition, the reaction mixture was heated to 55.degree. C. and
stirred at 55.degree. C. for a further 2 hours. Next, slowly and
with stirring, 184 parts by weight of
N,N-bis(3-trimethoxysilylpropan-1-yl)amine (Dynasylan.RTM. 1124
from Degussa) were added to the mixture. Stirring was then carried
out at 55.degree. C. for a further two hours. Thereafter free
isocyanate groups were no longer detectable by IR spectroscopy. The
resulting compound (A2) had a solids content of 89%. The surface
tension of the resulting compound (A2) was found by the ring method
to be 27.0 mN/m.
5.2. Preparation of a Surface-Modified Adduct (A3)
[0303] A reaction vessel equipped with stirrer, reflux condenser,
oil heating, and nitrogen inlet tube was charged with 100 parts by
weight of a commercial isocyanurate of hexamethylene diisocyanate
(Desmodur.RTM. N 3600 from Bayer AG). Added slowly to this initial
solution of the isocyanurate, with stirring, was a solution of 5
parts by weight of a carbinol-functional siloxane (Baysilone.RTM.
OF 502 6% from GE-Bayer Silicones) in 1.25 parts by weight of the
commercial aromatic solvent Solventnaphta.RTM.. Following the
addition, the reaction mixture was heated to 55.degree. C. and
stirred at 55.degree. C. for a further 2 hours. Next, slowly and
with stirring, 181 parts by weight of
N,N-bis(3-trimethoxysilylpropan-1-yl)amine (Dynasylan.RTM. 1124
from Degussa) were added to the mixture. Stirring was then carried
out at 55.degree. C. for a further two hours. Thereafter free
isocyanate groups were no longer detectable by IR spectroscopy. The
resulting compound (A3) had a solids content of 90%. The surface
tension of the resulting compound (A3) was found by the ring method
to be 26.5 mN/m.
5.3. Preparation of a Surface-Modified Adduct (A4)
[0304] A reaction vessel equipped with stirrer, reflux condenser,
oil heating, and nitrogen inlet tube was charged with 100 parts by
weight of a commercial isocyanurate of hexamethylene diisocyanate
(Desmodur.RTM. N 3600 from Bayer AG). Added slowly to this initial
solution of the isocyanurate, with stirring, was a solution of 10
parts by weight of a carbinol-functional siloxane (Baysilone.RTM.
OF 502 6% from GE-Bayer Silicones) in 2.5 parts by weight of the
commercial aromatic solvent Solventnaphta.RTM.. Following the
addition, the reaction mixture was heated to 55.degree. C. and
stirred at 55.degree. C. for a further 2 hours. Next, slowly and
with stirring, 175 parts by weight of
N,N-bis(3-trimethoxysilylpropan-1-yl)amine (Dynasylan.RTM. 1124
from Degussa) were added to the mixture. Stirring was then carried
out at 55.degree. C. for a further two hours. Thereafter free
isocyanate groups were no longer detectable by IR spectroscopy. The
resulting compound (A4) had a solids content of 91%. The surface
tension of the resulting compound (A4) was found by the ring method
to be 26.5 mN/m.
5.4. Preparation of a Hydroxyl-Containing Polyacrylate (PAC 2)
[0305] A reactor flushed with nitrogen and with a condenser
attached was charged with 17.5 parts by weight of pentyl acetate,
and this initial charge was heated to 140.degree. C. with stirring.
In parallel with this, two separate feed streams were prepared.
Feed stream 1 consisted of 28.58 parts by weight of 2-hydroxypropyl
methacrylate, 11.93 parts by weight of cyclohexyl methacrylate,
14.44 parts by weight of ethylhexyl methacrylate, 6.88 parts by
weight of ethylhexyl acrylate, and 0.15 part by weight of acrylic
acid. Feed stream 2 consisted of 2.945 parts by weight of
Solventnaphta.RTM. and 8.06 parts by weight of peroxide TBPEH
(=tert-butyl hydroperoxide). When the temperature of 140.degree. C.
had been reached, feed stream 2 was metered in slowly and uniformly
over a period of 285 minutes. 15 minutes after the start of feed
stream 2, feed stream 1 was metered slowly and uniformly into the
reactor over a period of 240 minutes. After the end of the metering
of feed stream 2, the reaction mixture was stirred at 140.degree.
C. for a further 120 minutes for postpolymerization. The solids
content of the resulting product was found to be 65%, the acid
number 5-7 mg KOH/g and the OH number 180 mg KOH/g (in each case
based on the solids) and the viscosity 19.5 dPas at 23.degree.
C.
5.5. Preparation of a Catalyst (C2) Based on an Amine-Blocked
Phosphoric Ester
[0306] A reactor equipped with a dropping funnel and a reflux
condenser was charged with 32.4 parts by weight of ethyl hexyl
phosphate and 50 parts by weight of methoxypropyl acetate and this
initial charge was homogenized. Subsequently, with cooling and
stirring, 17.6 parts by weight of triethylamine were added dropwise
at a rate such that the temperature did not exceed 60.degree. C.
Following addition of the triethylamine, the reaction mixture was
stirred at room temperature for 2 hours more. The resulting
reaction product had a solids content of 50.0%.
6. Preparation of 2-Component (2K) Clearcoat Materials
[0307] The raw materials set out in Table 5 were combined in
succession in the quantities indicated, and homogenized, in order
to prepare the millbase clearcoat materials.
TABLE-US-00006 TABLE 5 Composition of the 2-component clearcoats of
Examples 3 to 5 and of Comparative Example C7 Ingredient [parts by
weight] Example C7 Example 3 Example 4 Example 5 Polyacrylate 73.5
73.5 73.5 73.5 (PAC2) from 6.4. Butyldiglycol 8.5 8.5 8.5 8.5
acetate Butanol 0.15 0.15 0.15 0.15 Tinuvin 5941-R .sup.1) 1.86
1.86 1.86 1.86 Tinuvin 292 .sup.2) 0.24 0.24 0.24 0.24 Byk .RTM.
320 .sup.3) 0.15 0.15 0.15 0.15 Byk .RTM. 306 .sup.4) 0.20 0.20
0.20 0.20 Solventnaphta .RTM. 3 3 3 3 Butyl acetate 3.63 3.63 3.63
3.63 Ethoxypropyl 4.77 4.77 4.77 4.77 acetat Butylglycol 4 4 4 4
acetate Catalyst (C2) 0 2 2 2 from 5.5. Adduct (A2) 0 30 0 0 from
5.1. Adduct (A3) 0 0 30 0 from 5.2. Adduct (A4) 0 0 0 30 from 5.3.
Notes on Table 5: Tinuvin .RTM. 5941 - R = commercial mixtures of
different light stabilizers from Ciba Specialty Chemicals Inc.
Tinuvin .RTM. 292 = commercial light stabilizer based on sterically
hindered amines (HALS) from Ciba Specialty Chemicals Inc. Byk .RTM.
320 = commercial flow control additive based on a 52% strength
solution of a polyether-modified polymethylalkylsiloxane, from
Byk-Chemie GmbH, Wesel Byk .RTM. 306 = commercial flow control
additive based on a 12.5% strength solution of a polyether-modified
polydimethylsiloxane in 7/2 xylene/monophenylglycol, from
Byk-Chemie GmbH, Wesel
[0308] Immediately prior to application, 33 parts by weight of
curative were added to 100 parts by weight of millbase, and the
resulting mixture was homogenized. The curative used was prepared
by combining and homogenizing the ingredients listed in Table
6.
TABLE-US-00007 TABLE 6 Ingredient Parts by weight of curative
Basonat .RTM. HI 190 (product of BASF AG) 23 Desmodur .RTM. Z 4470
(70% in SN) 64 Butyl acetate 6.5 Solventnaphta .RTM. 6.5 Footnotes
to Table 6: Basonat .RTM. HI 190 = commercial isocyanurate of
hexamethylene diisocyanate from BASF AG, 90% in a mixture of
Solventnaphta .RTM. and butyl acetate Desmodur .RTM. Z 4470 =
commercial isocyanurate of isophorone diisocyanate from Bayer
Material Science AG, 70% in Solventnaphta .RTM.
7. Production of the Coatings
[0309] The individual 2K clearcoat materials were applied to metal
test panels which had each been coated with a typical, known,
cathodically deposited and thermally cured electrocoat, a typical,
known, thermally cured surfacer coat, and a film of a commercial,
conventional black basecoat material from BASF Coatings AG that had
been subjected to initial drying at 80.degree. C. for 10 minutes.
The basecoat film and the clearcoat film were cured together at
140.degree. C. for 22 minutes. The resulting basecoat had a film
thickness of 7.5 .mu.m, and the clearcoat a film thickness of 40
.mu.m
8. Investigation of the Properties of the Resulting Coatings
[0310] All of the surfaces were of high gloss and outstanding
appearance. The dry scratch resistance of the resulting surfaces
was determined by means of the crockmeter test (9 .mu.m paper
grade). This was done by operating along the lines of EN ISO 105-X
12 and evaluating the loss of gloss at 20.degree. C. after 10
double rubs.
TABLE-US-00008 TABLE 7 Crockmeter test Clearcoat of Clearcoat of
Clearcoat of Clearcoat of Test Example C7 Example 3 Example 4
Example 5 Residual 15% 55% 60% 66% gloss after crockmeter test
[%]
[0311] The results demonstrate that the dry scratch resistance of
the formulations can be increased significantly through the
addition of the adducts (A2) to (A4) together with the catalyst.
The experiments also show that the greater the amount of
surface-active adduct (A) employed, the more strongly pronounced
the effect.
[0312] The clearcoat films of Examples 4, 5, and C 7 were
investigated for their weathering over 6000 h in the so-called
WOM-CAM 180 Q/B test in accordance with VDA [German Automakers
Association] test sheet (E) 621-430 April 97 and/or SAE J1960 JUN89
(referred to below for short as the CAM 180 test). In the CAM 180
test it was found that all of the samples investigated exhibited no
cracking even after 6000 h. The gloss of Examples 4 and 5 after
6000 h was identical, within the bounds of measurement accuracy, to
the corresponding gloss from Example C 7. This demonstrates the
good weathering resistance of the modified 2K clearcoats.
* * * * *