U.S. patent application number 09/747471 was filed with the patent office on 2002-08-29 for two-component coating compositions containing silane adhesion promoters.
Invention is credited to Hergenrother, P. Richard, Roesler, Richard R..
Application Number | 20020119330 09/747471 |
Document ID | / |
Family ID | 25005191 |
Filed Date | 2002-08-29 |
United States Patent
Application |
20020119330 |
Kind Code |
A1 |
Roesler, Richard R. ; et
al. |
August 29, 2002 |
Two-component coating compositions containing silane adhesion
promoters
Abstract
The present invention relates to two-component coating
compositions containing a) a polyisocyanate component, b) an
isocyanate-reactive component and c) 0.1 to 20 wt. %, based on the
weight of components a) and b), of a compound containing
alkoxysilane groups and urea groups corresponding to the formula 1
wherein X represents identical or different organic groups which
are inert to isocyanate groups below 100.degree. C., provided that
at least one of these groups is an alkoxy group, Y represents a
linear or branched alkylene group containing 1 to 8 carbon atoms, R
represents the residue obtained by removing the isocyanate groups
from a monoisocyanate or a polyisocyanate, R.sub.1 and R.sub.2 are
identical or different and represent organic groups which are inert
to isocyanate groups at a temperature of 100.degree. C. or less,
R.sub.3 and R.sub.4 are identical or different and represent
hydrogen or organic groups which are inert to isocyanate groups at
a temperature of 100.degree. C. or less, and n has a value of 1 to
6. The present invention also relates to substrates coated with
these coating compositions, in particular metal substrates.
Inventors: |
Roesler, Richard R.;
(Wexford, PA) ; Hergenrother, P. Richard;
(Gibsonia, PA) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
25005191 |
Appl. No.: |
09/747471 |
Filed: |
December 22, 2000 |
Current U.S.
Class: |
428/447 ;
525/100 |
Current CPC
Class: |
Y10T 428/31663 20150401;
C08G 18/12 20130101; C08G 18/12 20130101; C08G 18/482 20130101;
C08G 18/792 20130101; C09D 175/08 20130101; C08G 18/0885 20130101;
C08G 18/3893 20130101; C08G 18/409 20130101; C08G 18/667 20130101;
C08G 18/12 20130101; C08G 18/7664 20130101 |
Class at
Publication: |
428/447 ;
525/100 |
International
Class: |
B32B 009/04; C08F
008/00 |
Claims
What is claimed is:
1. A two-component coating composition comprising a) a
polyisocyanate component, b) an isocyanate-reactive component and
c) 0.1 to 20 wt. %, based on the weight of components a) and b), of
a compound containing alkoxysilane groups and succinyl urea groups
corresponding to the formula 4wherein X represents identical or
different organic groups which are inert to isocyanate groups below
100.degree. C., provided that at least one of these groups is an
alkoxy group, Y represents a linear or branched alkylene group
containing 1 to 8 carbon atoms, R represents the residue obtained
by removing the isocyanate groups from a monoisocyanate or a
polyisocyanate, R.sub.1 and R.sub.2 are identical or different and
represent organic groups which are inert to isocyanate groups at a
temperature of 100.degree. C. or less, R.sub.3 and R.sub.4 are
identical or different and represent hydrogen or organic groups
which are inert to isocyanate groups at a temperature of
100.degree. C. or less and n has a value of 1 to 6.
2. The composition of claim 1 wherein R.sub.1 and R.sub.2 are
identical or different and represent alkyl groups having 1 to 9
carbon atoms, R.sub.3 and R.sub.4 represent hydrogen and n has a
value of 1 to 4.
3. The composition of claim 1 wherein component c) is present in an
amount of 0.5 to 10 wt. %, based on the weight of components a) and
b), and R.sub.1 and R.sub.2 are identical or different and
represent methyl, ethyl or butyl, R.sub.3 and R.sub.4 represent
hydrogen and n has a value of 1 to 4.
4. The composition of claim 1 wherein R represents the residue
obtained by removing the isocyanate groups from a monomeric
polyisocyanate or a polyisocyanate adduct.
5. The composition of claim 2 wherein R represents the residue
obtained by removing the isocyanate groups from a monomeric
polyisocyanate or a polyisocyanate adduct.
6. The composition of claim 3 wherein R represents the residue
obtained by removing the isocyanate groups from a monomeric
polyisocyanate or a polyisocyanate adduct.
7. The composition of claim 1 wherein polyisocyanate component a)
comprises an NCO prepolymer prepared from a polyisocyanate and a
polyether polyol and component b) comprises a polyhydroxyl
compound.
8. The composition of claim 2 wherein polyisocyanate component a)
comprises an NCO prepolymer prepared from a polyisocyanate and a
polyether polyol and component b) comprises a polyhydroxyl
compound.
9. The composition of claim 3 wherein polyisocyanate component a)
comprises an NCO prepolymer prepared from a polyisocyanate and a
polyether polyol and component b) comprises a polyhydroxyl
compound.
10. The composition of claim 4 wherein polyisocyanate component a)
comprises an NCO prepolymer prepared from a polyisocyanate and a
polyether polyol and component b) comprises a polyhydroxyl
compound.
11. The composition of claim 5 wherein polyisocyanate component a)
comprises an NCO prepolymer prepared from a polyisocyanate and a
polyether polyol and component b) comprises a polyhydroxyl
compound.
12. The composition of claim 6 wherein polyisocyanate component a)
comprises an NCO prepolymer prepared from a polyisocyanate and a
polyether polyol and component b) comprises a polyhydroxyl
compound.
13. The composition of claim 7 wherein component b) comprises a
polyether polyol.
14. The composition of claim 8 wherein component b) comprises a
polyether polyol.
15. The composition of claim 9 wherein component b) comprises a
polyether polyol.
16. The composition of claim 10 wherein component b) comprises a
polyether polyol.
17. The composition of claim 11 wherein component b) comprises a
polyether polyol.
18. The composition of claim 12 wherein component b) comprises a
polyether polyol.
19. A substrate coated with coating composition of claim 1.
20. A metal substrate coated with the coating composition of claim
1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to two-component coating
compositions containing adhesion promoters based on aspartate
silanes and to their use for preparing coatings having improved
adhesion, especially wet adhesion.
[0003] 2. Description of the Prior Art
[0004] Two-component coating compositions containing a
polyisocyanate component and an isocyanate-reactive component,
preferably a polyhydroxyl compound, are known and can be used to
coat a variety of substrates. One of the deficiencies of these
coatings is that they do not possess adequate wet adhesion, which
is a critical requirement for coatings used underground, e.g., as
coatings for oil and gas transmission pipelines.
[0005] Coatings previously used for this application have suffered
from other problems. Asphaltic coatings are biodegradable and not
suitable for long term (20 to 50 years) use. Coal tar coatings are
not used because of toxicity. Liquid epoxy coatings require
application temperatures of >55.degree. C. and cure too slowly
for production use in the field. Polyolefin coatings do not
maintain adhesion under cathodic protection.
[0006] High performance coatings are needed. Known polyurethane
coatings have the ability to be rapidly cured, but do not have the
wet adhesion necessary for this application.
[0007] Accordingly, it is an object of the present invention to
provide coating compositions that are suitable for preparing
coatings having improved adhesion, especially wet adhesion.
[0008] This object may be achieved with the two-component coating
compositions according to the present invention which contain
certain silane adhesion promoters. The silane compounds are
prepared by the reaction of compounds containing one or more
isocyanate groups with aspartate silanes as described
hereinafter.
[0009] The adhesion promoters used in the compositions of the
present invention are described in U.S. Pat. No. 5,908,948.
However, the compounds disclosed in the patent are used as coating
compositions; their use as adhesion promoters to improve the wet
adhesion of two-component coating compositions is not
disclosed.
[0010] The use of silanes as adhesion promotors has been suggested.
A product information bulletin from OSi Specialties discloses the
use of several silane compounds as adhesion promotors for various
coating resins, including polyurethanes. However, as shown by the
comparison examples of the present application, most of the
disclosed silane compounds were not very effective for improving
the adhesion, especially the wet adhesion, of two-component
polyurethane coating compositions. Accordingly, it is apparent that
the reference to polyurethanes was a reference to one-component,
fully reacted polyurethanes.
[0011] It must be regarded as surprising and unexpected that the
adhesion promoters according to the present invention provide good
adhesion, especially wet adhesion, since they contain less silane
per unit weight than the silane compounds disclosed in the OSi
bulletin when added in similar amounts. In addition, because they
contain less silane the adhesion promoters according to the
invention are less costly, thereby reducing the cost of the
resulting coating compositions.
SUMMARY OF THE INVENTION
[0012] The present invention relates to two-component coating
compositions containing
[0013] a) a polyisocyanate component,
[0014] b) an isocyanate-reactive component and
[0015] c) 0.1 to 20 wt. %, based on the weight of components a) and
b), of a compound containing alkoxysilane groups and urea groups
corresponding to the formula 2
[0016] wherein
[0017] X represents identical or different organic groups which are
inert to isocyanate groups below 100.degree. C., provided that at
least one of these groups is an alkoxy group,
[0018] Y represents a linear or branched alkylene group containing
1 to 8 carbon atoms,
[0019] R represents the residue obtained by removing the isocyanate
groups from a monoisocyanate or a polyisocyanate,
[0020] R.sub.1 and R.sub.2 are identical or different and represent
organic groups which are inert to isocyanate groups at a
temperature of 100.degree. C. or less,
[0021] R.sub.3 and R.sub.4 are identical or different and represent
hydrogen or organic groups which are inert to isocyanate groups at
a temperature of 100.degree. C. or less, and
[0022] n has a value of 1 to 6.
[0023] The present invention also relates to substrates coated with
these coating compositions, in particular metal substrates.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The compounds containing alkoxysilane groups that are used
as component c) in the compositions according to the present
invention are based on the reaction products of compounds
containing one or more isocyanate groups and compounds containing
alkoxysilane groups and aspartate groups (secondary amino groups)
corresponding to formula II) 3
[0025] The compounds of formula II are prepared by reacting
aminoalkyl alkoxysilanes corresponding to formula III)
H.sub.2N--Y--Si--(X).sub.3 (III)
[0026] with maleic or fumaric acid esters corresponding to formula
IV)
R.sub.1OOC--CR.sub.3.dbd.CR.sub.4--COOR.sub.2 (IV)
[0027] In formulas I to IV
[0028] X represents identical or different organic groups which are
inert to isocyanate groups below 100.degree. C., provided that at
least one of these groups is an alkoxy group, preferably alkyl or
alkoxy groups having 1 to 4 carbon atoms and more preferably alkoxy
groups;
[0029] Y represents a linear or branched alkylene group containing
1 to 8 carbon atoms, preferably a linear group containing 2 to 4
carbon atoms or a branched group containing 5 to 6 carbon atoms,
more preferably a linear group containing 3 carbon atoms,
[0030] R represents the residue obtained by removing the isocyanate
groups from a monomeric polyisocyanate, a polyisocyanate adduct or
an NCO prepolymer, preferably a monomeric polyisocyanate or a
polyisocyanate adduct,
[0031] R.sub.1 and R.sub.2 are identical or different and represent
organic groups which are inert to isocyanate groups at a
temperature of 100.degree. C. or less, preferably alkyl groups
having 1 to 9 carbon atoms, more preferably methyl, ethyl or butyl
groups,
[0032] R.sub.3 and R.sub.4 are identical or different and represent
hydrogen or organic groups which are inert towards isocyanate
groups at a temperature of 100.degree. C. or less, preferably
hydrogen, and
[0033] n has a value of 1 to 6, preferably 1 to 4.
[0034] With regard to the preceding definitions R.sub.1 and R.sub.2
may be different when the compounds of formula II) are prepared
from mixed maleates, such as methylethyl maleate. In addition, one
R.sub.1 may be different from another R.sub.1. For example, when a
mixture of compounds containing alkoxysilane groups (e.g. those
prepared from dimethyl and diethyl maleate) is used to prepare the
compounds of formula I), one pair of R.sub.1 and R.sub.2 groups
will be methyl and the other will be ethyl.
[0035] Especially preferred are compounds in which X represents
methoxy, ethoxy groups or propoxy groups, more preferably methoxy
or ethoxy groups and most preferably methoxy groups, and Y is a
propylene group.
[0036] Examples of suitable aminoalkyl alkoxysilanes of formula III
include 2-aminoethyl-dimethylmethoxysilane;
6-aminohexyl-tributoxysilane; 3-aminopropyl-trimethoxysilane;
3-aminopropyl-triethoxysilane; 3-aminopropyl-methyldiethoxysilane;
5-aminopentyl-trimethoxysilane; 5-aminopentyl-triethoxysilane and
3-aminopropyl-triisopropoxysilane. 3-aminopropyl-trimethoxysilane
and 3-aminopropyl-triethoxysilane are particularly preferred.
[0037] Examples of optionally substituted maleic or fumaric acid
esters suitable for use in the preparation of polyaspartates II)
include dimethyl, diethyl, dibutyl (e.g., di-n-butyl), diamyl,
di-2-ethylhexyl esters, the previously discussed mixed maleates and
fumarates, and the corresponding maleic or fumaric acid esters
substituted by methyl in the 2- and/or 3-position. The dimethyl,
diethyl and dibutyl esters of maleic acid are preferred and the
diethyl and dibutyl esters are especially preferred.
[0038] The reaction of primary amines with maleic or fumaric acid
esters to form aspartates is disclosed in U.S. Pat. Nos. 5,126,170,
5,236,741 and 5,364,955 (the disclosures of which are herein
incorporated by reference). The compounds of formula II are
colorless to pale yellow. They may be reacted with polyisocyanates
to form the compounds of formula I without further
purification.
[0039] Suitable isocyanates for preparing the compounds of formula
I are selected from monoisocyanates, monomeric polyisocyanates,
polyisocyanate adducts and NCO prepolymers, preferably monomeric
polyisocyanates and polyisocyanate adducts. The polyisocyanates
have an average functionality of 1.8 to 6, preferably 2 to 6 and
more preferably 2 to 4.
[0040] Suitable monomeric diisocyanates may be represented by the
formula
R(NCO).sub.2
[0041] in which R represents an organic group obtained by removing
the isocyanate groups from an organic diisocyanate having a
molecular weight of about 112 to 1,000, preferably about 140 to
400. Diisocyanates preferred for the process according to the
invention are those in which R represents a divalent aliphatic
hydrocarbon group having 4 to 40, preferably 4 to 18 carbon atoms,
a divalent cycloaliphatic hydrocarbon group having 5 to 15 carbon
atoms, a divalent araliphatic hydrocarbon group having 7 to 15
carbon atoms or a divalent aromatic hydrocarbon group having 6 to
15 carbon atoms.
[0042] Examples of the suitable organic diisocyanates include
1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate,
2,2,4-trimethyl-1,6-hexamethylene diisocyanate,
1,12-dodecamethylene diisocyanate, cyclohexane-1,3- and
-1,4-diisocyanate, 1-isocyanato-2-isocyanatomethyl cyclopentane,
1-isocyanato-3-isocyanatome- thyl-3,5,5-trimethyl-cyclohexane
(isophorone diisocyanate or IPDI),
bis-(4-iso-cyanatocyclohexyl)-methane, 2,4'-dicyclohexyl-methane
diisocyanate, 1,3- and 1,4-bis-(isocyanatomethyl)-cyclohexane,
bis-(4-isocyanato-3-methyl-cyclohexyl)-methane,
.alpha.,.alpha.,.alpha.',- .alpha.'-tetramethyl-1,3- and/or
-1,4-xylylene diisocyanate,
1-isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane, 2,4-
and/or 2,6-hexahydrotoluylene diisocyanate, 1,3- and/or
1,4-phenylene diisocyanate, 2,4- and/or 2,6-toluylene diisocyanate,
2,4- and/or 4,4'-diphenyl-methane diisocyanate, 1,5-diisocyanato
naphthalene and mixtures thereof.
[0043] Suitable monoisocyanates include compounds corresponding to
the formula R--NCO, wherein R is defined as above.
[0044] Polyisocyanates containing 3 or more isocyanate groups such
as 4-isocyanantomethyl-1,8-octamethylene diisocyanate and aromatic
polyisocyanates such as 4,4',4"-triphenylmethane triisocyanate and
polyphenyl polymethylene polyisocyanates obtained by phosgenating
aniline/formaldehyde condensates may also be used.
[0045] Preferred organic diisocyanates include 1,6-hexamethylene
diisocyanate,
1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane
(isophorone diisocyanate or IPDI),
bis-(4-isocyanato-cyclohexyl)-methane,
1-isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane, 2,4-
and/or 2,6-toluylene diisocyanate, and 2,4- and/or
4,4'-diphenylmethane diisocyanate.
[0046] Suitable polyisocyanate adducts for preparing the compounds
of formula I are those prepared from the preceding monomeric
polyisocyanates and containing isocyanurate, uretdione, biuret,
urethane, allophanate, iminooxadiazine dione, carbodiimide and/or
oxadiazinetrione groups. The polyisocyanates adducts, which
preferably have an NCO content of 5 to 30% by weight, include:
[0047] 1) Isocyanurate group-containing polyisocyanates which may
be prepared as set forth in DE-PS 2,616,416, EP-OS 3,765, EP-OS
10,589, EP-OS 47,452, U.S. Pat. No. 4,288,586 and U.S. Pat. No.
4,324,879. The isocyanato-isocyanurates generally have an average
NCO functionality of 3 to 3.5 and an NCO content of 5 to 30%,
preferably 10 to 25% and most preferably 15 to 25% by weight.
[0048] 2) Uretdione diisocyanates which may be prepared by
oligomerizing a portion of the isocyanate groups of a diisocyanate
in the presence of a suitable catalyst, e.g, a trialkyl phosphine
catalyst, and which may be used in admixture with other aliphatic
and/or cycloaliphatic polyisocyanates, particularly the
isocyanurate group-containing polyisocyanates set forth under (1)
above.
[0049] 3) Biuret group-containing polyisocyanates which may be
prepared according to the processes disclosed in U.S. Pat. Nos.
3,124,605; 3,358,010; 3,644,490; 3,862,973; 3,906,126; 3,903,127;
4,051,165; 4,147,714; or 4,220,749 by using co-reactants such as
water, tertiary alcohols, primary and secondary monoamines, and
primary and/or secondary diamines. These polyisocyanates preferably
have an NCO content of 18 to 22% by weight and an average NCO
functionality of 3 to 3.5.
[0050] 4) Urethane group-containing polyisocyanates which may be
prepared in accordance with the process disclosed in U.S. Pat. No.
3,183,112 by reacting excess quantities of polyisocyanates,
preferably diisocyanates, with low molecular weight glycols and
polyols having molecular weights of less than 400, such as
trimethylol propane, glycerine, 1,2-dihydroxy propane and mixtures
thereof. The urethane group-containing polyisocyanates have a most
preferred NCO content of 12 to 20% by weight and an (average) NCO
functionality of 2.5 to 3.
[0051] 5) Allophanate group-containing polyisocyanates which may be
prepared according to the processes disclosed in U.S. Pat. Nos.
3,769,318, 4,160,080 and 4,177,342. The allophanate
group-containing polyisocyanates have a most preferred NCO content
of 12 to 21% by weight and an (average) NCO functionality of 2 to
4.5.
[0052] 6) Isocyanurate and allophanate group-containing
polyisocyanates which may be prepared in accordance with the
processes set forth in U.S. Pat. Nos. 5,124,427, 5,208,334 and
5,235,018, the disclosures of which are herein incorporated by
reference, preferably polyisocyanates containing these groups in a
ratio of monoisocyanurate groups to mono-allophanate groups of
about 10:1 to 1:10, preferably about 5:1 to 1:7.
[0053] 7) Iminooxadiazine dione and optionally isocyanurate
group-containing polyisocyanates which may be prepared in the
presence of special fluorine-containing catalysts as described in
DE-A 19611849. These polyisocyanates generally have an average NCO
functionality of 3 to 3.5 and an NCO content of 5 to 30%,
preferably 10 to 25% and most preferably 15 to 25% by weight.
[0054] 8) Carbodiimide group-containing polyisocyanates which may
be prepared by oligomerizing di- or polyisocyanates in the presence
of known carbodiimidization catalysts as described in DE-PS
1,092,007, U.S. Pat. No. 3,152,162 and DE-OS 2,504,400, 2,537,685
and 2,552,350.
[0055] 9) Polyisocyanates containing oxadiazinetrione groups and
containing the reaction product of two moles of a diisocyanate and
one mole of carbon dioxide.
[0056] Preferred polyisocyanate adducts are the polyisocyanates
containing isocyanurate, uretdione, biuret, iminooxadiazine dione
and/or allophanate groups.
[0057] The NCO prepolymers, which may also be used to prepare the
compounds of formula I, are prepared from the previously described
monomeric polyisocyanates or polyisocyanate adducts, preferably
monomeric diisocyanates, and polyhydroxyl compounds containing at
least two hydroxyl groups. These polyhydroxyl compounds include
high molecular weight compounds having molecular weights of 500 to
about 10,000, preferably 800 to about 8,000, and more preferably
1800 to 8,000, and optionally low molecular weight compounds having
molecular weights below 500. The molecular weights are number
average molecular weights (M.sub.n) and are determined by end group
analysis (OH number). Products obtained by reacting polyisocyanates
exclusively with low molecular weight compounds are polyisocyanates
adducts containing urethane groups and are not considered to be NCO
prepolymers.
[0058] Examples of the high molecular weight compounds are
polyester polyols, polyether polyols, polyhydroxy polycarbonates,
polyhydroxy polyacetals, polyhydroxy polyacrylates, polyhydroxy
polyester amides and polyhydroxy polythioethers. The polyether
polyols, polyester polyols and polycarbonate polyols are preferred.
Especially preferred are the polyether polyols.
[0059] Examples of suitable high molecular weight polyhydroxyl
compounds include polyether polyols, which may be obtained in known
manner by the alkoxylation of suitable starter molecules. Examples
of suitable starter molecules include polyols, water, organic
polyamines having at least two N--H bonds and mixtures thereof.
Suitable alkylene oxides for the alkoxylation reaction are
preferably ethylene oxide and/or propylene oxide, which may be used
in sequence or in admixture.
[0060] Also suitable for preparing the prepolymers are polyester
polyols prepared from low molecular weight alcohols and polybasic
carboxylic acids such as adipic acid, sebacic acid, phthalic acid,
isophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid,
maleic acid, the anhydrides of these acids and mixtures of these
acids and/or acid anhydrides. Polylactones having hydroxyl groups,
particularly poly-.epsilon.-caprolactone, are also suitable for
producing the prepolymers.
[0061] Other suitable polyols include polycarbonates having
hydroxyl groups, which may be produced by the reaction of diols
with phosgene or diaryl carbonates such as diphenyl carbonate.
[0062] Further details concerning the low molecular weight
compounds and the starting materials and methods for preparing the
high molecular weight polyhydroxy compounds are disclosed in U.S.
Pat. No. 4,701,480, herein incorporated by reference.
[0063] These NCO prepolymers preferably have an isocyanate content
of 0.3 to 35% by weight, more preferably 0.6 to 25% by weight and
most preferably 1.2 to 20% by weight. The NCO prepolymers are
produced by reacting the diisocyanates with the polyol component at
a temperature of 40 to 120.degree. C., preferably 50 to 100.degree.
C., at an NCO/OH equivalent ratio of 1.3:1 to 20:1, preferably
1.4:1 to 10:1. If chain extension via urethane groups is desired
during the preparation of the isocyanate prepolymers, an NCO/OH
equivalent ratio of 1.3:1 to 2:1 is selected. If chain extension is
not desired, an excess of diisocyanate is preferably used,
corresponding to an NCO/OH equivalent ratio of 4:1 to 20:1,
preferably 5:1 to 10:1. The excess diisocyanate may optionally be
removed by thin layer distillation when the reaction is completed.
In accordance with the present invention NCO prepolymers also
include NCO semi-prepolymers which contain unreacted starting
polyisocyanates in addition to the urethane group-containing
prepolymers.
[0064] The compounds of formula I containing alkoxysilane groups
and urea groups are prepared by reacting the polyisocyanate
monomers and/or adducts with the compounds of formula II at an
equivalent ratio of aspartate groups (i.e., secondary amino groups)
to isocyanate groups of approximately 1:1. The reaction is
preferably carried out by incrementally adding the aspartate to the
polyisocyanate. The reaction to form the urea groups is conducted
at a temperature of 10 to 100.degree. C., preferably 20 to
80.degree. C. and more preferably 20 to 50.degree. C.
[0065] In accordance with the present invention the urea groups
initially formed by the reaction of the compounds containing
alkoxysilane groups and aspartate groups of formula II with the
polyisocyanate may be converted to hydantoin groups in known
manner, e.g., by heating the compounds at elevated temperatures,
optionally in the presence of a catalyst. Therefore, the term "urea
groups" is also intended to include other compounds containing the
group, N--CO--N, such as hydantoin groups.
[0066] Suitable polyisocyanates for use as component a) in the
compositions of the present invention are selected from the
polyisocyanates previously described for use in the preparation of
the compounds of formula I), preferably polyisocyanate adducts and
NCO prepolymers and more preferably NCO prepolymers.
[0067] Suitable isocyanate-reactive components for use as component
b) in the compositions of the present invention are the high and
low molecular weight, polyols previously disclosed for preparing
the NCO prepolymers. Also suitable are the known high molecular
weight amine-functional compounds, which may be prepared by
converting the terminal hydroxy groups of the polyols previously
described to amino groups, and the high molecular weight
polyaldimines disclosed in U.S. Pat. No. 5,466,771, herein
incorporated by reference. The high molecular weight polyols are
preferred.
[0068] The two-component coating compositions of the present
invention may be prepared by mixing the individual components.
Components a) and b) are present in an amount of sufficient to
provide an equivalent ratio of isocyanate groups is
isocyanate-reactive, preferably hydroxyl groups of 0.8:1 to 1.2:1,
preferably 0.9:1 to 1.1:1 and more preferably 1:1 to 1.1:1.
Component c) is present in an amount of 0.1 to 20%, preferably 0.5
to 10%, more preferably 0.5 to 5% and most preferably 1 to 3%,
based on the weight of components a) and b).
[0069] The two-component compositions generally may be either
solvent-free or contain up to 70%, preferably up to 60% organic
solvents, based on the weight of components a) and b). Suitable
organic solvents include those which are known from polyurethane
chemistry.
[0070] The compositions may also contain known additives, such as
catalysts, leveling agents, wetting agents, flow control agents,
antiskinning agents, antifoaming agents, fillers (such as silica,
aluminum silicates and high-boiling waxes), viscosity regulators,
plasticizers, pigments, dyes, UV absorbers and stabilizers against
thermal and oxidative degradation.
[0071] The two-component compositions may be applied to any desired
substrates, such as wood, plastics, leather, paper, textiles,
glass, ceramics, plaster, masonry, metals and concrete. They may be
applied by standard methods, such as spray coating, spread coating,
flood coating, casting, dip coating, roll coating. The coating
compositions may be clear or pigmented.
[0072] The two-component compositions are especially suitable for
coating substrates, preferably metal substrates such as pipes,
which will be exposed to a wet environment.
[0073] The two-component compositions may be cured at ambient
temperature or at elevated temperatures, preferably at ambient
temperatures.
[0074] The invention is further illustrated but is not intended to
be limited by the following examples in which all parts and
percentages are by weight unless otherwise specified.
EXAMPLES
[0075] Polyisocyanate 1
[0076] An aniline/formaldehyde condensation product containing
44.4% 4,4'-diphenylmethane diisocyanate, 19.0% 2,4'-diphenylmethane
diisocyanate, 2.6% 2,2'-diphenylmethane diisocyanate and the
remainder higher functional homologs, and having an isocyanate
content of 32.6% and a viscosity at 25.degree. C. of about 41
mPa.s.
[0077] Polyisocyanate 2
[0078] An isocyanurate group-containing polyisocyanate prepared
from 1,6-hexamethylene diisocyanate and having an isocyanate
content of 21.6%, a content of monomeric diisocyanate of <0.2%
and a viscosity at 25.degree. C. of 3000 mPa.s (available from
Bayer Corporation as Desmodur N 3300).
[0079] Polyisocyanate 3
[0080] 556 g of a distilled diphenylmethanediisocyanate (MDI)
composition containing 65% 2,4'-MDI and 35% 4,4'-MDI were stirred
at 60.degree. C. Then a mixture of 222 g of a polyether diol made
by propoxylation of propylene glycol (OH number 112) and 222 g of a
tetrafunctional polyether made by propoxylation of ethylene diamine
(OH number 60) was added dropwise, so that a maximum temperature of
65.degree. C. was maintained. When an NCO content of 16% was
reached, the prepolymer was diluted with 1000 g of a crude MDI
containing 40.5% 2,4-MDI, 49,5% 4,4'-MDI and 10% polymeric MDI. The
final semi-prepolymer had an NCO content of 24% and a viscosity of
220 mPa.s at 23.degree. C.
[0081] Polyether polyol 1
[0082] A polypropylene oxide polyol having a functionality of 3, an
OH number of 370 and an equivalent weight of 152 and initiated with
trimethylolpropane.
[0083] Polyether polyol 2
[0084] A polypropylene oxide polyol initiated with glycerine,
tipped with ethylene oxide (PO:EO equivalent ratio 83:17), having a
functionality of 3, an OH number of 35 and an equivalent weight of
1600 and containing 20% of the equimolar reaction product toluene
diisocyanate and hydrazine (overall OH number 28).
[0085] Silane Aspartate 1
[0086] 1482 parts (8.27 equiv.) of 3-aminopropyltrimethoxysilane
were added to a 5 liter flask fitted with agitator, thermocouple,
nitrogen inlet and addition funnel with condenser. 1423.2 parts
(8.27 equiv.) of diethyl maleate were added dropwise through the
addition funnel over a period of 2 hours. The temperature of the
reactor was maintained at 25.degree. C. during the addition. The
reactor was maintained at 25.degree. C. for an additional 5 hours
at which time the product was poured into glass containers and
sealed under a blanket of nitrogen. After one week the unsaturation
number was 0.6 indicating the reaction was .about.99% complete. The
product, N-(3-trimethoxysilylpropyl) aspartic acid diethyl ester,
had a viscosity of 11 mPa.s at 25.degree. C.
[0087] Compound 1 containing alkoxysilane groups of formula I
[0088] 367 parts (1 equiv.) of silane aspartate 1 and 129 parts (1
equiv.) of polyisocyanate 1 were added to a three neck, 1 liter,
round bottom flask fitted with agitator, thermocouple, nitrogen
inlet and condenser. The reaction to form the urea groups was
accompanied by an exotherm. A water bath was used to maintain the
temperature at 80.degree. C. for 3 hours until an IR spectrum
showed no residual isocyanate in the urea product.
[0089] Compound 2 containing alkoxysilane groups of formula I
[0090] 669 parts (1.7 equiv.) of silane aspartate 1 and 331 parts
(1.7 equiv.) of polyisocyanate 2 were added to a three neck, 5
liter, round bottom flask fitted with agitator, thermocouple,
nitrogen inlet and condenser. The reaction to form the urea groups
was accompanied by an exotherm which took the reaction mixture to
80.degree. C. The reaction was held at 80.degree. C. for 14 hours
until an IR spectrum showed no residual isocyanate in the urea
product.
[0091] Compound 3 containing alkoxysilane groups of formula I
[0092] 100 parts (0.254 equiv.) of silane aspartate 1 and 21.4
parts (0.254 equiv.) of 1,6-hexamethylene diisocyanate were added
to a three neck, 500 ml flask fitted with agitator, thermocouple,
nitrogen inlet and condenser. The reaction to form the urea groups
was accompanied by an exotherm which took the reaction mixture to
80.degree. C. The reaction was held at 80.degree. C. for 3 hours
until an IR spectrum showed no residual isocyanate in the urea
product.
[0093] Two-component coating compositions
[0094] Two-component coating compositions were prepared from the
following ingredients:
1 Parts Component I Polyether polyol 1 120 Polyether polyol 2 60
1,4-butane diol 130 3,5-diethyl-toluene diamine 5 Talc 125 Lamilar
silicate.sup.1 70 Titanium dioxide 30 1:1 Blend of molecular
sieve/caster oil.sup.2 50 Dibutyltin dilaurate 0.4 Silicone flow
aid 0.2 Component II Polyisocyanate 3 490 Silane additive See Table
Black paste 5 .sup.1Novacite 207 (available from Malvern)
.sup.2Baylith L paste (available from Bayer)
[0095] Two-component coating compositions were prepared from the
preceding ingredients and the amounts and types of the silane
additives set forth in the following tables. The compositions were
applied at 20-30 mils on hot-rolled, sand-blasted steel panels. The
panels were cured at room temperature for two weeks.
[0096] To determine dry and wet adhesion the coated panels were
placed on end in a container or water such that about two thirds of
the coating was submerged. After 30 days the panel was removed and
immediately tested. The test was conducted by scribing an "X" on
both the dry and wet areas of the panel. A knife was used to pick
at the corners of the "X." A rating scale of 1 to 10 was used as
follows:
[0097] 1--no adhesion, coating falls off of panel
[0098] 5--moderate adhesion, but coating can be peeled off of
panel
[0099] 7--strong adhesion, but coating can be peeled off of
panel
[0100] 8--coating tears as it is peeled off of panel
[0101] 10--coating can only be cut off of panel
[0102] A rating of 7 is acceptable, a rating of 8 is a good result
and a rating of 10 is an excellent result. A rating of 6 or less is
unacceptable for use as a pipeline coating.
2TABLE 1 According to the Invention Amount Adhesion Adhesion
Promoter (wt. %) Dry Wet Compound 1 containing alkoxysilane groups
1 10 10 2 -- 10 3 10 10 5 10 10 10 8 9 15 10 10 Compound 2
containing alkoxysilane groups 1 -- 8 2 -- 9 3 8 9 5 9.5 9 10 8 9
15 10 10 Compound 3 containing alkoxysilane groups 5 7 8 10 8 8 20
8 7
[0103]
3TABLE 2 Comparison Examples Amount Adhesion Adhesion Promoter (wt.
%) Dry Wet None 0 2 2 3-isocyanatopropyltriethoxysilane.sup.3 1 7 7
Tris-[3-(trimethoxysilyl)propyl]isocyanurate.sup.4 1 8 8 2 -- 10 3
9 8.5 5 8 9 10 7 8 15 7 7.5
3-glycidoxypropyl-trimethoxysilane.sup.5 1 10 10 2 10 10
3-mercaptopropyl-trimethoxysilane.sup.6 1 3 3 2 3 7
3-aminopropyl-trimethoxysilane.sup.7 1 3 6 2 10 10
N-(2-aminoethyl)-3-aminopropyl- 1 2 2 trimethoxysilane.sup.8 2 3 5
Triaminofunctionalsilane.sup.9 1 3 3 2 incom incom.sup.10
3-ureidopropyl-trialkoxysilane.sup.11 1 3 3 2 4 3
Bis-(3-trimethoxysilylpropyl)amine.sup.12 1 3 3 2 8 6 Silquest Wet
Link 78 additive 1 4 5 2 8 9
[0104] 3--Silquest A-1310
[0105] 4--Silquest Y-11597
[0106] 5--Silquest A-187
[0107] 6--Silquest A-189
[0108] 7--Silquest A-1110
[0109] 8--Silquest A-1120
[0110] 9--Silquest A-1130
[0111] 10--Incompatible
[0112] 11--Silquest A-1160
[0113] 12--Silquest A-1170
[0114] The examples demonstrate that it is possible using the
adhesion promoters according to the present invention to match and
even exceed the adhesion provided by the known silane adhesion
promoters, while at the same time lowering the cost of the
additives.
[0115] Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
* * * * *