Note: Descriptions are shown in the official language in which they were submitted.
2102170
-
Herberts Gesellschaft mit beschr~nkter Haftung
An aqueous vehicle composition coatina media containing this
com~osition and their use
This invention relates to an aqueous coating medium which is
suitable for the production of base-, clear- and covering
lacquer coatings, extender layers and primer coats,
particularly in the production of multilayer coatings in the
motor vehicle industry.
Coating media are known which are based on acidic CH compounds
and olefinically unsaturated compounds. For example, EP-A-0
224 158 describes two-component lacquers which contain
components of this type. These two-component lacquers can be
thermally hardened; the hardening reaction is catalysed by
Lewis and/or Bronsted bases. Acetoacetate polymers as
crosslinking agents for acryloyl-unsaturated acrylates are
described in EP-A-0 027 454. Systems of this type are
suitable for the production of various coatings. These two-
component lacquers still contain appreciable amounts of
solvent and therefore possess disadvantages from the point of
view of current environmental policies.
The object of the present invention is the preparation of a
vehicle composition which is suitable for the production of
aqueous coating media with a low solvent content and which can
be hardened rapidly at low temperatures, e.g. at room
temperature, to form films of good hardness and good
` resistance to water and solvents.
It has been shown that this object can be achieved by means
of an aqueous vehicle composition, which forms one subject to
which the present invention relates, and which contains~
~ , . . .
:
2102170
A) 10 - 90 weight % of one or more compounds acting as
crosslinking agents with an average of at least two
acidic CH hydrogen atoms and
B) 10 - 90 weight % of one or more (meth)acrylic
copolymers, polyester- and/or polyurethane resins
suitable for the Michael addition, with at least two
~,B-unsaturated groups bonded via the carbonyl carbon
atom of
1 0 0 0 o : . ~
Il 11 ~I I .
-C-, -C-O- and/or -C-N-, with a C=C equivalent weight of
85 - 1800 and a number average molecular weight (Mn) of
170 - 10,000 g/mole,
wherein the equivalent ratio of A:B is 2:1 to 1:2;
C) 0.01 - 5 weight %, based on the sum of the weights of ;
components A) and B), of a catalyst in the form of a `
; 20 Lewis or Bronsted base, wherein the conjugate acids of ~ ~- the latter have a pKa value of at least 10, `
and also water, and optionally solvents, pigments, extenders,
and the usual lacquer auxiliary process materials and/or
additives.
The aqueous vehicle compositions according to the invention ~ -
can be processed to form aqueous coating media which in
addition to the vehicle composition contain one or more
organic solvents, and optionally pigments and/or extenders
and/or the usual lacquer additives. They may optionally also -~
contain other vehicle components.
~;, : .,:: :.
The acidic CH crosslinking agents used as component A) in the
coating media according to the invention preferably comprise
~ . .
those which contain at least two acidic CH hydrogen atoms
;~ which originate from one or more of the following groupings,
which may be the same or different:
.
I
-'` 21~170
W3 - CH - W2
I
Wl
o O O
Il 11 11 1 \
wherein W1 = -C-, -C-O-, C-N-, -P=O, -CN or NO2
O o o
Il ll I~ I \ .. .:
W2 = -C-, -C-O-, -C-N-, -P=0 or -CN,
O O o
Il 11 11 1 :-,
W3 = -C-, -C-0-, -C-N-, -H, alkyl or alkyls, ;
,
wherein the alkyl and alkyls preferably have 1 to 6 C atoms
and wherein the carboxyl or carbonamide groupæ defined above
:
for the W1, W2 and/or W3 radicals are each bonded via the
carbon atom to the CH group and the CH group is bonded via at
least one of the W1, W2 and/or W3 radicals to a polymeric or
~ oligomeric unit. The acidic CH functionality of component A)
r`~ ; amounts on average to > 2 per molecule. Therefore, when W3
^~ 30 in the above general formula denotes a hydrogen atom, one
group of this type is sufficient, since it has two acidïc
hydrogen atoms.
As`mentioned above, the acidic CH functionality of component
A? is on average > 2. This means that monofunctional molecules
mày also be used in admixture with molecules of higher
functionality.
.~. .,: ,
,~ The acidic C~ crosslinking compounds are preferably
,~ 40 substantially free from primary, secondary or tertiary amino
groups, since these can have a negative effect on storage
stability and light-fastness.
, ~ ~
~ ~.
~` 2102~ 70
Examples of acidic CH crosslinking components A) which
correspond to the above general formula are given below.
These examples are subdivided below into three groups: A1, A2,
and A3.
Group A1 contains components with an average of at least two
groups with active hydrogen atoms, of the type
- C - H,
I
in the molecule, which are derived from methanecarboxylic acid
monoamide units or acetoacetic acid ester-2-carboxylic acid
amides.
Examples of suitable A1 compounds comprise reaction products
of malonic acid, such as malonic acid dimethyl, diethyl,
dibutyl or dipentyl esters, or acetoacetic acid esters, such
as acetoacetic acid methyl, ethyl, butyl or pentyl esters,
with polyisocyanates.
Examples of isocyanates of this type which may be used
according to the invention comprise (cyclo)aliphatic or
aromatic polyisocyanates such as tetramethylene diisocyanate,
hexamethylene diisocyanate, 2,2,4-trimethylene diisocyanate,
1,12-dodecane diisocyanate, cyclohexane 1,3- and 1,4-
diisocyanates, 1-isocyanato-3,3,5-trimethyl-5-isocyanato-
methylcyclohexane (= isophorone diisocyanate;IPDI), perhydro-
2,4'- and/or4,4'-diphenylmethane diisocyanate, phenylene 1,3-
,
and 1,4-diisocyanates, toluene 2,4- and 2,6-diisocyanates,
diphenylmethane 2,4'- and/or 4,4'-diisocyanate, 3,2'- and/or
3,4-diisocyanato-4-methyl-diphenylmethane, naphthalene 1,5-
diisocyanate, triphenylmethane 4,4'-triisocyanate,
tetramethylxylylene diisocyanate or mixtures of these
compounds.
;~
~ "
-- 21~2170
In addition to these simple isocyanates, other isocyanates
which contain heteroatoms in the radical linking the
isocyanate groups are also suitable. Examples of these
include carbodimide groups, allophanate groups, isocyanurate
groups, urethane groups, acylated urea groups and
polyisocyanates containing biuret groups.
The known polyisocyanates which are mainly used in the
production of lacquers are particularly suitable for the
process according to the invention, e.g. modification products
of the above-mentioned simple polyisocyanates which contain
biuret, isocyanurate or urethane groups, particularly tris-(6-
isocyanatohexyl)-biuret or polyisocyanates containing low
molecular weight urethane groups, such as those which can be
obtained by the reaction of IPDI present in excess with simple
polyhydric alcohols with molecular weights in the range 62-
300, particularly trimethylolpropane. Any mixtures of the
above-mentioned polyisocyanates may also of course be used for
the production of the products according to the invention. -
Other suitable polyisocyanates comprise the known prepolymers
containing terminal isocyanate groups, such as those which are
obtainable by the reaction of the above-mentioned simple
polyisocyanates, primarily diisocyanates, with
substoichiometric amounts of organic compounds with at least
two groups which are capable of reacting with isocyanate
groups. Isocyanates such as these which are preferably used
comprise compounds with a total of at least two amino groups
and/or hydroxyl groups, and with a number average molecular
weight of 300 to 10,000, preferably 400 to 6000. The
corresponding polyhydroxyl compounds are preferably used, e.g. ~-
the hydroxypolyesters, hydroxpolyethers and/or the acrylic
resins containing hydroxyl groups which are known in the art
in polyurethane chemistry.
In these known prepolymers the ratio of isocyanate groups to
hydrogen atoms which are reactive towards NCO corresponds to
.
~ ` 2~2170
1.05 to 10:1, preferably 1.1 to 3:1, the hydrogen atoms
preferably originating from hydroxyl groups.
In addition, the type and quantitative proportions of the
starting materials used in the preparation of the NCO
prepolymers are preferably selected so that the NCO
prepolymers a) have an average NCO functionality of 2 to 4,
preferably of 2 to 3, and b) have a number average molecular
weight of 500 - 10,000, preferably of 800 - 4000.
Reaction products of monoisocyanates with esters and partial
esters formed between polyhydric alcohols and malonic acid are
also suitable as Al compounds, however. Examples of
polyhydric alcohols include dihydric to pentahydric alcohols
such as ethanediol, the various propane-, butane-, pentane-
and hexanediols, polyethylene- and polypropylene diols,
glycerine, trimethylolethane and -propane, pentaerythritol,
hexanetriol and sorbitol. Examples of suitable
monoisocyanates include aliphatic isocyanates such as n-butyl
isocyanate, octadecyl isocyanate, cycloaliphatic isocyanates
such as cyclohexyl isocyanate, aryl-aliphatic isocyanates such
as benzyl isocyanate or aromatic isocyanates such as phenyl
isocyanate.
Also suitable are the corresponding malonic esters of acrylic
resins containing OH groups, polyesters, polyurethanes,
polyethers, polyester amides and imides and/or the reaction
products of malonic acid half esters such as malonic acid
monoethyl ester with aliphatic and aromatic epoxy resins, e.g.
acrylate resins containing epoxide groups, glycidyl ethers of
polyols such as hexanediol, neopentyl glycol,
diphenylolpropane and -methane and hydantoins containing
glycidyl groups. Mixtures of these compounds are also
suitable.
. .
` 21~2170
The examples of Group A2 given below comprise a suitable
hardener component with active CH groups, which contains at
least two groups corresponding to formula (I)
X
\
CH - K -
~:
or structural units corresponding to formula (I') or (I'') : :~
[ - X ' - CH -- K ' ] (I ' ~ [ X ' - f~H - K ' ] (I ' ' ) ~ ;
y,
:~
where K represents
O O
C or C - O,
and where the latter group is bonded via the C atom to the CH
. group;
,:~
X and Y are the same or different
Rl ll
~: CO2R1, CN, NO2, CONH2, CONHRlH, CONR1R1, wherein the R1
radicals may be the same or different and represent a
hydrocarbon radical, preferably an alkyl radical with 1 to 12,
most preferably 1 to 6 C atoms, which may also be interrupted
by oxygen or an N-alkyl radical, subject to the proviso that
only one of the two radicals X, Y may represent an N02 group;
` ::
. O o
~ 35 K' = C or C - O, :
`~ wherein the latter group is bonded to the CH group via the C
~ atom;
'. ' ~;:
~; ' ~: ,
21021 7~
X', Y' are the same or different
O ~:
C - O or C - N,
subject to the proviso that when K' and X' represent ~ :~
::
C - o ., ~ ~
the Y' radical is not the same as ~ -
C - N .
The number of groups (I) in the hardener according to the
invention is preferably 2 to 200, most preferably 2 to 10, the
larger numbers relating to oligomeric or polymeric products
and representing average values here.
The hardener components A2 which can be used according to the
invention preferably correspond to formula (II)
~:. /X
l CH - K -J R2
:~ ~Y / n
`~
`~ where X, Y and K have the meanings given above, R2 represents
~-` a polyol radical
:~ O
~:1 R2 (OH)n (K a ~ _ O)
~'~ or a polycarboxylic acid radical R2 :~
:~ 35
~` R2 (CO2H)n (K = C) , :
` ' ~ ', ' ~' :'
. ~
~ .
2102~7~
g ,
and n is at least 2, preferably 2 to 200, most preferably 2
to lO. In the case of oligomeric or polymeric hardener
components these numbers are again average values.
Also preferred are hardener components which fall within Group
A2 and which are obtained by the alcoholysis of compounds of
formula (III) or formula (IV)
R102 C ~ R102 C ~
CH - K _ Rl (III) / CH - K _ xl (IV)
X R102C
with polyols R2(OH) n~ where X, K and Rl have the meanings
given above.
The above-mentioned polyols R2(OH)n may be polyhydric alcohols
which preferably contain 2 to 12, most preferably 2 to 6,
carbon atoms. Examples of these include: ethylene glycol,
1,2-, and 1,3-propylene glycol, 1,4- and 2,3-butylene glycol,
20 di-B-hydroxyethyl butanediol, 1,6-hexanediol, 1,8-octanediol,
neopentyl glycol, 1,6-cyclohexanediol, 1,4-bis-
(hydroxymethyl)-cyclohexane, 2,2-bis-(4-hydroxycyclohexyl)-
propane, 2,2-bis-(4-~-hydroxyethoxy)phenylpropane, 2-methyl-
1,3-propanediol, glycerine, trimethylolpropane, 1,2,6-
` 25 hexanetriol, 1,2,4-butanetriol, tris-(B-hydroxyethyl)-
isocyanurate, trimethylolethane, pentaerythritol and their
~;~ hydroxyalkylation products, and also diethylene glycol, -~
triethylene glycol, tetraethylene glycol, polyethylene
glycols, dipropylene glycol, tripropylene glycol, ~
30 polypropylene glycols, dibutylene glycol, polybutylenegly¢ols- ~ ;
; and xylynene glycol. Moreover, polyesters can be used which
are obtained from or using lactones, e.g. ~-caprolactones, or
hydroxycarboxylic acids, such as hydroxypivalic acid, ~-
hydroxydecanoic acid, ~-hydroxycaproic acid or thioglycollic
35 acid, for example. In the case of polyhydric alcohols of this
~ type, the subscript n in the above formula (II) preferably
-~ represents 2 to 4.
; .:
21021~0 ;~
Alternatively, the polyol may comprise an oligomeric or
polymeric polyol compound (polyol resin), the number average
molecular weight of which (determined by gel chromatography
using polystyrene as the calibration standard) is usually in
the range from about 170 to 10,000, preferably about 500 to
about 5000. However, in special cases the molecular weight
may be 10,000 and above. The oligomers/polymers comprise
polymerides, condensation polymers or addition polymer
compounds. Their hydroxyl number is generally 30 to 250,
preferably 45 to 200, most preferably 50 to 180 mg KOH/g.
These compounds, which contain OH groups, may also optionally
contain other functional groups such as carboxyl groups.
Examples of polyols of this type include polyether polyols,
polyacetal polyols, polyester amide polyols, polyamide
polyols, epoxy resin polyols or their reaction products with
C02, phenol resin polyols, polyurea polyols, polyurethane
polyols, polyols of cellulose esters and ethers, partially
saponified homo- or copolymers of vinyl esters, partially
acetalated polyvinyl alcohols, polycarbonate polyols,
polyester polyols or acrylic resin polyols. Polyether
polyols, polyester polyols, acrylic resin polyols and
polyurethane polyols are preferred. Polyols of this type,
~- which may also be used in admixture, are described in DE-A-31
24 784, for example.
. .
Examples of polyurethane polyols include those which are
formed by the reaction of di- and polyisocyanates with an
excess of di- and/or polyols. Examples of suitable
isocyanates include hexamethylene diisocyanate, isophorone
diisocyanate, toluene diisocyanate and also isocyanates formed
` from three moles of a diisocyanate such as hexamethylene
diisocyanate or isophorone diisocyanate, and biurets produced
from the reaction of one mole of a diisocyanate with one mole
~ 35 of water. Suitable polyurea polyols may be obtained in a
: similar manner by the reaction of di- and polyisocyanates with
.
;
.~ 21~21 rl f~
ll
equimolar amounts of aminoalcohols, e.g. ethanolamine or
diethanolamine.
Examples of polyester polyols include the known
polycondensation products of di- or polycarboxylic acids or
their anhydrides, such as phthalic anhydride, adipic acid,
etc., and polyols such as ethylene glycol, trimethylolpropane,
glycerine, etc.
lo Suitable polyamide polyols may be obtained in a similar manner
to the polyesters, by replacing the polyols at least in part
by polyamines such as isophorone diamine, hexamethylene
diamine, diethylene triamine, etc.
Examples of polyacrylate polyols or polyvinyl compounds
containing OH groups include the known copolymers obtained
from (meth)acrylic acid esters containing hydroxyl groups or
vinyl alcohol and other vinyl compounds, such as styrene or
(meth)acrylic acid esters, for example.
The above polycarboxylic acids R2(CO2H)n, where n is
preferably 2 to 4 here, may be of an aliphatic,
cycloaliphatic, aromatic and/or heterocyclic nature, and may
optionally be substituted and/or saturated, by halogen atoms
for example. Examples of carboxylic acids such as these and
their derivatives include: succinic acid, adipic acid, suberic
acid, azelaic acid, sebacic acid, phthalic acid, terephthalic
acid, isophthalic acid, trimellitic acid, pyromellitic acid,
tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexane
1,3- and 1,4-dicarboxylic acids, di- and tetrachlorophthalic
acids, endomethylene tetrahydrophthalic acid and its
hexachloro derivative, glutaric acid, maleic acid, fumaric
acid, dimeric and trimeric fatty acids such as oleic acid,
optionally in admixture with monomeric fatty acids or cyclic
monocarboxylic acids such as benzoic acid, p-tert.-butyl
bènzoic acid or hexahydrobenzoic acid, and also the reaction
-: .
210217~
12
products of the above-mentioned polyols R2(OH) n with cyclic
carboxylic acid anhydrides.
Depending on the type of the polyol or polycarboxylic acid
component, the hardener components A2 which can be used
according to the invention comprise more or less viscous
liquids, or solids which are substantially soluble at least
in the usual lacquer solvents and which preferably contain
less than 5 weight %, most preferably less than 1 weight %,
of crosslinked constituents. The CH equivalent weight, which
is a measure of the amount of groups (I) or structural units
(I')l(II ") in (A2), is generally between 100 and 5000,
preferably between 200 and 2000, and the number average
molecular weight (Mn) is generally 200 to 10,000, preferably
500 to 5000 (determined by gel chromatography using
polystyrene as the calibration standard). Methods of
preparing compounds such as these are described in more detail
in EP-A-O 310 011.
Additional examples of hardener components which can be used
according to the invention are those of Type A3, in which the
CH grouping is derived from a compound containing a -Co-CHR3-
~; CO-, NC-CHR3-Co, NC-CH2-CN, =Po-CHR3-Co-, =Po-CHR3-CN, =PO-
CHR3-Po= or -Co-CHR3-No2 grouping, wherein R3 is preferably a
Cl - C8 alkyl or H, most preferably hydrogen. B-dioxo
compounds are preferred.
The above A3 groupings may be bonded to at least one
polyvalent monomeric or polymeric compound. For example, they
~may be bonded to at least one compound of the group comprising
monohydric or polyhydric alcohols, polymers containing OH
groups, polyamines and polymercaptans. They are polyvalent
with respect to their CH function. They may be prepared, for
example, by the esterification of a polyepoxide with a -CH
carboxylic acid forming the grouping, e.g. acetoacetic acid.
An A3 component with two active H atoms for each epoxide
` 210217~3
13
group is obtained in this manner. Aromatic or aliphatic
polyepoxides may be used for this purpose.
Examples of suitable compounds of the A3 type include ketones
such as acetylacetone, benzoyl acetone or acetyl
dibenzoylmethane; esters of optionally alkyl-substituted
acetoacetic acid such as ~- and/or ~-methyl acetoacetic acid
or of acetone dicarboxylic acid; malonic acid units of malonic
acid with ester-like bonds, and their monoalkyl derivatives,
either straight-chain or branched, with 1 to 6 C atoms in the
alkyl radical, e.g. methyl, ethyl and n-butyl and also phenyl;
or esters of cyanoacetic acid with monohydric to hexahydric
alcohols with 1 to 10 C atoms. The alkyl-substituted esters,
e.g. ~-methyl or ~,~-dimethyl acetoacetic ester, have only one
active H atom and are therefore preferably used in the form
of di- or polyesters of polyhydric alcohols, in order to make
a sufficient number of reactive groups available. Examples
of suitable alcohols for the esterification of the above acids
include methanol, ethanol, butanol, octanol and/or polyhydric
alcohols or polyhydroxy compounds, the latter two types being
preferred. Further examples of A3 compounds include
acetoacetic ester, ethanediol-bis-acetoacetic ester,
glycerine-tris-malonic acid ester, trimethylolpropane-tris-
acetoacetic ester, partial esters of these acids with
polyhydric alcohols, and also the corresponding esters of OH
group-containing acrylic resins, polyesters, polyethers,
polyester amides and imides, polyhydroxylamines, and also
nitriles of these acids inasmuch as these exist, e.g. malonic
acid mono- or dinitrile, alkoxycarbonyl methanephosphonic acid
and the corresponding bis-methanephosphonic acid esters. ! The
above-mentioned acids may also be bonded in the form of amides
to amines, preferably polyamines, which may also comprise
oligomers and/or polymers, including amine resins, aliphatic
amines being preferred.
If polyamines are used as the starting materials, the A3
compounds can be prepared in the form of amides. For example
- :
21021 7i~
14
the starting material may comprise 1 mole o~` an alkylene
diamine, which is reacted with 2 moles of acetoacetic ester
with the formation of a compound which also has four H atoms
activated by amide groups.
Reactive nitro compounds are also suitable as A3 compounds,
e.g. nitroacetic acid derivatives such as tri-(nitroacetic
acid)-glycerine ester or trimethylolpropane nitroacetic acid
ester.
Examples of A3 compounds which form -CH- type groups include
diketene and its monoalkyl substitution products, and also
tetrahydrodioxin, which can react with suitable components
with the formation of acetoacetic ester or amide groups.
The hardener components A) may be prepared in the usual
solvents. It is advantageous if solvents are used which do
not impair the subsequent production of the coating medium.
It is also advantageous if the content of organic solvents is
kept as low as possible. If the hardener component A)
contains polar groups, e.g. amide or urethane groupings, it
is possible to disperse it easily in water. This may
optionally be assisted if the crosslinking components contain
ionic groups which can be neutralised, e.g. carboxyl groups,
in the oligomer or polymer skeleton. Crosslinking agents with
ionic groups such as these may be dispersed in water well.
At the same time, the content of organic solvents can be
reduced to a low value without significantly increasing the
viscosity of the crosslinking agent solution.
(Meth)acrylic copolymers or polyester- and/or polyurethane
resins, which are suitable for the Michael addition and which
are as defined above, are used according to the invention as
component B). They contain at least two groups capable of
participating in the Michael addition, i.e. groups which
contain double bonds activated by at least one negatively
polarising group (Michael acceptor). These comprise ~,B-
2102~'~0
unsaturated groups which can be incorporated in the chains of
the copolymers or resins. They may also preferably be side
groups and/or terminal groups. Suitable B) compounds are
described in DE-PS-835 809, in US-PS-4,408,018 and in EP-A- -
16 16 79 and EP-A- 22 41 58, for example, to which reference
is made here. These are compounds (B) with at least two
groups corresponding to the formula
R5R4C = CR4- Z (V)
' `'
in which:
R5 represents hydrogen or a hydrocarbon radical, preferably ;~
an alkyl radical with 1 to 12, most preferably 1 to 4, -
C atoms such as a methyl, ethyl, n-propyl, iso-propyl,
n-butyl or tert.-butyl group;
R4 denotes entities which are the same or different,
representing hydrogen, a hydrocarbon radical, preferably
an alkyl radical with 1 to 10, most preferably 1 to 4,
C atoms, an ester group -C02Rl, a -CN, -NO2, -S02-, -
CONHRl, -CONRlRl or -CORl group, wherein the Rls are the
same or different and are as defined above for formula ~ - -
I; and
` 25
: o o o : :,
Z represents -C-, -~ - O, or -C - N- , :~
wherein the two latter groups are bonded to the CR4
group via the C atom.
RS and R4 in the above R5R4-C group preferably each represent ~ ~
hydrogen. -
The above groups V are indirectly bonded to each other. The
indirect linkage concerned may be a hydrocarbon radical, for
example, but is preferably the radical of a polyhydric alcohol
2~02~ ~ ~
16
or of a polyvalent amine or aminoalcohol. At the same time,
this indirect linkage may also be part of the chain of an
oligomer and/or polymer, i.e. the group V may exist in the
side chains of the oligomers or polymers or may form these
side chains.
According to a particular embodiment, the compound B)
corresponds to the formula
(R5R4C = CR4 -z) R2 (VI)
in which R5, R4 and Z have the same meaning as in formula (V),
R2 has the same meaning as in formula (II) and m is at least
2, preferably 2 to 200.
The R5R4C = CR4- Z group - (V) may be derived from a singly or
poly-unsaturated mono- or dicarboxylic acid with 2 to 20,
preferably 3 to 10, C atoms, for example.
Examples of carboxylic acids such as these include crotonic
acid and citraconic acid or their anhydrides, sorbic acid,
fumaric acid, mesaconic acid, substituted and unsubstituted
cinnamic acids, dihydrolevulinic acid, malonic acid
mononitrile, a-cyanacrylic acid, alkylidene malonic acid,
alkylidene acetoacetic acid, and preferably acrylic acid,
methacrylic acid and/or maleic acid or their anhydrides. The
linkage of the Michael acceptor to the bonding component which
is possible via the group Z or also via the R4 radical may be
effected via ester, amide, urethane or urea groups, as in a
polymeric carrier.
In accordance with the above, the groups corresponding to
formula (V) may be bonded to the radical of a polyol, a
polyamine, a polyamide or a polyiminoamide, wherein this
radical may also be an oligomer or polymer.
The polyols concerned here are basically the same as those
listed in detail above in connection with the Michael donor,
i.e. polyhydric alcohols or oligomeric or polymeric polyol
~~' 2ln2l7n
compounds, e.g. polyether polyols, polyester polyols, acrylic
resin polyols and polyurethane polyols.
The amino group-containing carriers (polyamines) comprise, for
example, the above-mentioned alkylene diamines and their
oligomers, such as ethylene diamine, propylene diamine,
butylene diamine, diethylene triamine, tetramine and higher
homologues of these amines, and also amino alcohols such as
diethanolamine or the like.
Examples of compounds suitable as component B) include: alkyl
glycol di(meth)acrylates such as ethylene glycol diacrylate,
diethylene glycol diacrylate, propylene glycol diacrylate,
trimethylene glycol diacrylate, neopentyl glycol diacrylate,
1,3-butylene glycol diacrylate, 1,4-butylene glycol
diacrylate, 1.6-hexamethylene glycol diacrylate, 1,10-
decamethylene glycol diacrylate, trimethylolpropane
triacrylate, pentaerythritol tetraacrylate, pentaerythritol
triacrylate and the corresponding methacrylates, and
alkoxylated and propoxylated derivatives.
Moreover, the ~,~-unsaturated group which is bonded via a
carbonyl carbon atom may be bonded to polymers, e.g.
condensation polymers such as polyesters or addition polymers
such as polyurethanes, polyethers or (meth)acrylic copolymers
or vinyl polymers, such as glycidyl (meth)acrylate copolymers.
Polymers which should be mentioned here by way of example
include urethane acrylates, obtained by the reaction of
polyisocyanate such as hexamethylene diisocyanate with
hydroxyalkyl acrylates suc~ as hydroxyethyl acrylate, or by
the reaction of hydroxyl group-containing polyesters,
polyethers or polyacrylates with polyisocyanates and
hydroxyalkyl acrylates, urethane acrylates obtained by the
reaction of caprolactonediol or -triol with polyisocyanates
and hydroxyalkylacrylates, polyether acrylates obtained by the
esterification of hydroxypolyethers with acrylic acid,
polyester acrylates obtained by the esterification of
.,. :. ~ , -. . ,
f.~.~ ,. . , . ~ . : :
2102~70
18
hydroxypolyesters with acrylic acid, polyacrylates obtained
by the reaction of acrylic acid with vinyl polymers containing
epoxide groups, e.g. copolymers of glycidyl (meth)acrylate or
vinyl glycidyl ether. The term "(meth)acrylic" is to be
understood, both here and below, as representing acrylic
and/or methacrylic.
Mixtures of the above compounds may also be used as component
B).
The C=C equivalent weight of component B) is 85 to 1800, for
example, preferably 180 to 1200, and the number average
molecular weight (Mn) is 170 to 10,000, for example;
preferably 500 to 5000.
The vehicle compositions according to the invention may also
contain 2-acetoacetoxy-ethyl(meth)acrylate as a reactive
diluent for adjusting the viscosity.
The coating medium according to the invention comprises a
mixture of the acidic CH crosslinking component A) and the
vehicle B). Mixtures of different components A) or B) may
also be used. The vehicles are compatible with each other and
may optionally contain solvents to improve their miscibility.
The preferred solvents for this purpose are those which do not
subsequently have a negative effect in the lacquer.
The ratio of the two components A) and B) depends upon the
number of available acidic C-H hydrogen atoms in the
crosslinking component and on the number of unsaturated groups
of the ~ unsaturated bond. Since the reactive groups can
be determined titrimetrically, accurately adjusted
stoichiometric mixture ratios can be achieved. The equivalent
ratio of the acidic CH groups to the ~,~-unsaturated groups
is preferably 0.75:1 to 1.25:1. By this means a sufficient
density of crosslinking is generally obtained. --
2 ~ ~ 2 ~
19
The elasticity of the crosslinked product can be controlled
within a range of tolerance, e.g. by means of the chain length
of the oligomers and/or polymers used for A) and B). The
oligomers and/or polymers used may thus be selected according
to the desired elasticity of the crosslinked product. The
degree of crosslinking can be controlled via the functionality
of the compounds A) and B) which are used. Thus the degree
of crosslinking can be increased when three or more reactive
groups are present in at least one of the compounds A) and B).
Component C) consists of catalysts in the form of Lewis bases
or Bronsted bases, the conjugate acids of the latter having
a pKa value of at least 10. Component C) may consist of one
or more catalysts. Examples of Lewis bases which have proved
to be particularly suitable include those of the
cycloaliphatic amine group such as diazabicyclooctane (DABCO),
tert.-aliphatic amines such as triethylamine, tripropylamine,
N-methyl diethanolamine, N-methyl diisopropylamine or N-butyl
diethanolamine, and amidines such as diazabicycloundecene
(DBU) and guanidines such as N,N,N'N'-tetramethyl guanidine.
Other examples include alkyl- or aryl-substituted phosphanes
such as tributyl phosphane, triphenyl phosphane, tris-p-tolyl
phosphane, methyl diphenyl phosphane, and hydroxy- and
aminofunctionalphosphanessuchastris-hydroxymethylphosphane
and tris-dimethylamino ethyl phosphane.
Examples of Bronsted bases which may be used include
alcoholates such as sodium or potassium ethanolate, quaternary
ammonium compounds such as alkyl-, aryl- or benzyl ammonium
hydroxides or halides, such as tetraethyl or
tetrabutylammonium hydroxide or fluoride for example, and
trialkyl or triaryl phosphonium salts or hydroxides.
The amount of catalysts is generally 0.01 to 5 weight %,
preferably 0.02 to 2 weight %, based on the total solids
content of components A) and B).
210217~
The crosslinking component A) and the vehicle component B) or
the mixtures thereof are used in agueous form according to the
invention.
For this purpose the crosslinking component A) and the vehicle
component B) are converted into an aqueous phase, optionally
with a low proportion of solvents and optionally together with
emulsifying agents. The preferred solvents are those which
are miscible with water. The amount of solvent may be up to
20 weight % for example, preferably up to 10 weight %, based
on the final aqueous composition. Ionic or non-ionic
emulsifying agents, preferably non-ionic emulsifying agents,
may be used as the emulsifying agents. The content of
emulsifying agent may be 0.5 to 30 weight % for example,
preferably between 1.5 and 15 weight %, based on the solids
content of component A) and component B) in the final aqueous
coating medium.
The usual methods familiar to one skilled in the art may be
employed for the preparation of the aqueous dispersions.
Thus, for example, the solvent-containing forms of components
A) and B) or mixtures thereof may be substantially freed from
solvents, preferably by distillation under reduced pressure,
whereupon the emulsifying agent can be dispersed therein,
preferably in the resins or resin mixtures whilst the latter
are still warm and of low viscosity. This mixture can then
be added to the aqueous phase, with intensive mixing for
example. The preparation of the dispersion may also be
assisted by heating the aqueous phase. Examples of suitable
mixer units include high speed stirrers or rotor/stator
mixers. It is also possible to improve the quality of the
dispersion by means of high-pressure or ultrasonic
homogenisers. -
.
Components A) and B) may be mixed first and then emulsified
together. However the crosslinking component A) and the ;~
-` 2~02~
21
vehicle component B) may of course be emulsified separately
and then mixed.
::
The process may be carried out continuously or batch-wise.
The dispersions produced may also be mixed with each other at
this time. An aqueous oil-in-water dispersion is obtained
which is stable on storage and which can be adjusted with
water to give solids contents which are suitable for
application. The aqueous dispersions obtained according to
the invention may have a solids content in the range of 25 -
55 weight %, for example, based on the final dispersion. They
may optionally be diluted with water before their application,
e.g. to a viscosity suitable for spraying.
:
Commercially available ionic or non-ionic emulsifying agents
are suitable as emulsifying agents. For example, the reaction
products of alkyl phenols with alkylene oxides may be used,
as may the reaction products of sorbitane fatty acid esters
with alkylene oxides, e.g. C1 -C12 alkylphenol ethoxylates.
As a rule, component C) is water-soluble, but can be
;~ emulsified as described if required.
The vehicle compositions according to the invention comprise
so-called two-component systems.
Components A) and B) are stored jointly as the vehicle
component 1 and component C) is stored as the hardener
component 2. If necessary, it is also possible to store
component B) as the vehicle component 1 and components A) and
C) as the hardener component 2, as long as A) and C) do not
react with each other.
This means that components 1 and 2 are stored separately and
are only mixed before or on their use, for the production of
coating media, for example.
~ .
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210217 ~3
22
The coating media according to the invention may be produced
by the usual methods familiar to one skilled in the art. For
the production of coating media, the usual industrial lacquer
additives may optionally be added to the crosslinking and
vehicle components which are used according to the invention.
Examples of such additives include anti-crater agents, anti-
foaming agents, flow media, anti-settling agents, viscosity
regulators, W stabilisers and bonding agents. The properties
affecting application and film formation can be influenced by
the amount of additives.
Known pigments and/or extenders may optionally also be
incorporated in the coating media. The relevant methods, e.g.
dispersion or milling, have frequently been described in the
lS literature. The usual pigments for clear or covering lacquers
are suitable as pigments, for example carbon black, titanium
dioxide, finely dispersed silica, aluminium silicate, French
chalk, organic and inorganic colorant pigments, transparent
colcrants, metallic pigments or crosslinked polymer
microparticles. Primers, extenders, metallic lacquers,
coloured covering lacquers or clear lacquers may be produced ~-
depending on the pigment selected.
In addition to water, the coating media according to the
invention may contain non-reactive co-solvents. These serve
to adjust the viscosity on application and to influence the
flow behaviour, and also to achieve a given lacquer effect.
Examples of such solvents include aromatic hydrocarbons, e.g.
xylenes; aliphatic hydrocarbons, e.g. n-hexane or cyclohexane;
ketones, such as acetone or methyl isopropyl ketone for
example; esters, such as butyl acetate or ethyl acetate, for
example; and ethers, such as methoxypropanol or
butoxypropanol, for example. However, alcohols may also be
used, such as isopropanol, hexanol or ethyl glycol, for
example. The properties relating to application and flow
behaviour can be influenced by the boiling point or the
different dissolving powers of the solvents. The amount of
-' :'
23 2102~7 ~ :
solvent added thus depends on the desired properties,
particularly on the viscosity properties, of the coating
medium. True solutions, emulsions or dispersions are formed
when water is used as the solvent. Coating media which
contain water have a particularly low content of volatile
organic solvents.
The coating media produced from the vehicles according to the
invention may be adjusted to the desired viscosity for
application by correspondingly re~ulating the addition of
water and/or additives.
Depending on the quantitative proportion of component 1 to
component 2, on the equivalent weight and on the amount of
catalyst, the coating media can be adjusted to give a pot life
between a few minutes and several hours.
The coating media produced in this manner may be applied in
the usual way, for example by immersion, spraying, brushing
or by an electrostatic route.
The coatings produced from the coating media may be hardened
over a broad temperature range, from +5C to 180C, for
example. The temperature range is preferably 20C to 180C,
for example room temperature.
The coating media produced from the vehicles according to the
invention are suitable for coatings which adhere to a
multiplicity of substrates, such as wood, textiles, plastics,
glass, ceramics, and metals in particular. The coating media
may also be used in a multilayer process. For example, they
may be applied to the usual primers, base lacquers or
extenders, or to covering lacquers which already exist. The
vehicles according to the invention are particularly suitable
for base lacquer, covering lacquer and clear lacquer
~` compositions.
24 2~0217~3
One preferred embodiment comprises the application of the
coating medium according to the invention as a clear lacquer
overcoat on to an aqueous base lacquer according to the
invention. In this connection, a wet-in-wet procedure may be
employed, or the base lacquer may be previously dried by
heating. This results in the bonding of both layers being
particularly good.
A particularly preferred area of application for the vehicles
according to the invention is the preparation of coating media
for coatings in the motor vehicle industry. The favourable
hardening conditions of the coating media produced from the
vehicles according to the invention make them particularly
suitable for motor vehicle repair coatings also.
Accordingly, the present invention also relates to a process `
for the production of coatings on various substrates, in which
a coating medium produced from the vehicle according to the ~;
invention is applied, and then dried and hardened. The
present invention also relates to the use of the vehicle
compositions according to the invention in primers, base
lacquers, covering lacquers and clear lacquers.
.
The following examples serve to explain the invention. All ~ -
parts (pts.) and percentages (%) are given by weight. `~
Example 1
Preparation of acetoacetic ester-functionalised component 1
670 pts. trimethylolpropane and 1950 pts. acetoacetic ester
were placed in a 4 litre three-necked flask fitted with a
stirrer, reflux condenser, thermometer and dropping funnel.
The mixture was heated with stirring until ethanol was split
off. After 4 hours, 488 g distillate was obtained; the
temperature was 175C. A vacuum was applied and the
` distillation was continued until a total of 806 g distillate
:~ .
25 2102170
was obtained. The acetoacetic ester-functional component 1
produced then had a theoretical solids content of 96.5 ~, a
viscosity of 172 mPas and an acid number of 131.6 mg KOH/g
solid resin.
In the following, trimethylolpropane triacrylate tTMPTA) was
used as the polyacryloyl compound.
Example 2
Preparation of an aqueous emulsion from components 1 and 2
(emulsion 3).
155.2 g of a 10 % aqueous solution of an emulsifying agent
based on a polyoxypropylene polyoxyethylene sorbitanic acid
diester were placed in a 1 litre flask at 60C. The mixture
was stirred using a stirrer rotating at a speed of about 7500
revolutions per minute. A mixture of 198.3 pts. of the
acetoacetic ester-functionalised component 1 and 151.7 pts.
TMPTA was added at 60C over three minutes. 50 g
demineralised water were added. The milky-white emulsion ~ -~
obtained had a solids content of 66.1 %.
Exam~le 3 -~
Preparation of an aqueous base lacquer: ~
: -: .::
a) 100 pts. of the aqueous emulsion 3) were homogenised
with 23.61 pts. demineralised water and 24.9 pts. of a
commercially available 3 % thickener paste (rheologi¢al
additive) with intensive stirring.
;~ b) 4.77 pts. of a 65 % solution of a commercially available
aluminium paste in white spirit/demineralised water
(17.5 %/17.5 %), 3.74 pts. butyl glycol, 0.35 pts. of a
` commercially available corrosion inhibitor to prevent
gassing of the aluminium, 0.7 pts. N-methyl pyrrolidone
26 210217 0
and 2.34 pts. butanol were mixed separately. The
mixture was adjusted to a spraying viscosity of 20"
using demineralised water.
Example 4
Preparation of an aqueous clear lacquer~
a) 49.1 pts. of the aqueous emulsion 3) were mixed with 10
10pts. of a commercially available thickener and 40.9 pts.
demineralised water, and then homogenised with 100 pts.
of a 10 % solution of DBU in demineralised water,
followed by adjusting to a spraying viscosity of 20".
Example 5
~ ' ,
The base lacquer from Example 3 was applied by spraying to a
metal sheet provided with a commercially available two- -
component polyurethane extender, aerated for 35 minutes at
room temperature, and the clear lacquer from Example 4 was
then applied. The sample was aerated again for 40 minutes and
then stoved at 60C for 45 minutes.
The film obtained had a good hardness, exhibited good flop and
good body and gloss.
,
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