Note: Descriptions are shown in the official language in which they were submitted.
` 2~02169
Herberts Gesellschaft mit beschrankter Haftung
Coating media and their use for the production of acid-
resisting coatinqs
This invention relates to a coating medium which is suitable
for the production of acid-resisting coatings, particularly
clear- and covering lacquer coatings, and which is suitable,
for example, for the production of multilayer coatings in the
motor vehicle industry.
Increasingly heavy demands are being made on the coatings used
for vehicles. In addition to high gloss and mechanical
resistance, to stone impact for example, resistance to petrol
and oil is required. Additional demands occur in the context
of the changing environment, such as the so-called "acid
rain". The coatings industry is therefore subjected to the
requirement of producing coating media for acid-resisting
coatings and coatings which withstand other aggressive
conditions, such as the long-term effects of animal excrement.
The increased demand for acid-resistance also leads to more
stringent test methods. Whereas lacquers were previously
tested using dilute acetic acid, the effect of up to 40 %
sulphuric acid, in part at an increased temperature of up to
70C, is now being investigated. As far as possible, the
protective effect and the appearance of the lacquer should
not change in the areas tested under these conditions. At
most, onIy a sIight roughness of the surface may occur due to
extreme acidic exposure of this type.
Another point of view which the coatings industry has to ~ake
into consideration is exposure to physiologically hazardous
substances, e.g. carcinogens and mutagens. Compounds which
are not completely harmless include isocyanates and aromatic
solvents, for example. On exposure to lacquer vehicles based
~: .
'1:- ~ : : .:
~ . . .
210216~
on lacquer systems which crosslink via free isocyanate groups,
volatile reactive isocyanates can constitute a hazard to
operating personnel. Skin contact with isocyanate-containing
coating media should also be avoided.
For these reasons there are developments aimed at avoiding the
use of reactive isocyanates in coating media, particularly in
the motor vehicle industry. EP-A-0 034 720 describes
oxazolidine-containing acrylate resins which crosslink with
water or atmospheric moisture to form films. However, this
system has the disadvantage that the hardening surface opposes
the deeper penetration of water into the lower lacquer layers
and prevents complete hardening there. Vehicle systems are
disclosed in EP-A-0 050 249, for example, which comprise
silicon-containing polymers. These polymers can react with
moisture and crosslink via groups on the silicon atom which
are susceptible to hydrolysis. These systems have the
disadvantage that the crosslinking is dependent on the
relative atmospheric humidity. On the other hand, it has to
be ensured that no moisture can reach the coating medium
during storage, since otherwise it can no longer be processed.
US-A-4 408 018 describes acrylic polymers into which ~-
acetoacetate groups have been introduced. The latter should
25 crosslink with a,~-unsaturated esters. Strong bases are -~
; required as catalysts for this crosslinking reaction. These
remain in the coating film after hardening and have an adverse -
effect on the properties of the coating, e.g. yellowing or
clouding of clear lacquer films may occur.
DE-A-35 41 140, EP-A-0 160 824 and EP-A-0 310 011 describe
~` hardener components and vehicle systems for the coatings
industry. These comprise solvent-containing two-component
systems (2K systems) which are produced based on a
35 polyunsaturated acrylate resin and a hardener component with -
active CH, NH or SH groups. In order to achieve rapid,
adequate crosslinking, compounds with a catalytic effect are
``' ~ ~. :
, , ~
21021fi9 :
- : :
required in the lacquer system. Examples of catalysts which
are used include: tertiary amines, amidines, guanidines,
phosphanes and halides of quaternary ammonium compounds. The
amount of catalysts may be up to 5 weight %. They are
necessary in order to accelerate the hardening reaction; this
can be assisted by an elevated temperature.
: ~:
The known coating media have to be used as two-component
systems. They contain catalytically active compounds and
cannot therefore be formulated as single-component systems (lK
systems). The maximum pot lives of catalyst-containing two-
component systems, which are mixed immediately before
application, are 48 hours; this means that thereafter the
coating media can no longer be used. When these known coating
media are used as clear or covering lacquers, they exhibit a
reduced stability towards yellowing on exposure to light. In
addition, the known coating media do not comply with the
above-mentioned more stringent criteria for acid-resistance.
The prior unpublished German Patent Application P 41 33 704.2 -~ :
describes a catalyst-free single-component coating medium in
which a crosslinking agent with at least two acidic CH
hydrogen atoms crosslinks with an acryloyl-functional
compound. -
The object of the present invention is the production of a
coating medium which is free from reactive isocyanate, and
which results in coatings which satisfy the more stringent
requirements relating to acid-resistance and which do not
exhibit yellowing.
`i It has been shown that this object can be achieved by means
of a catalyst-free system which can be formulated as a single-
component system and which contains~
:
.,, . ':
2~02169
A) 10 - 90 weight ~ of one or more compounds acting as
crosslinking agents with an average of at least two
groups capable of alcoholysis,
5 B) 10 - 90 weight ~ of one or more (meth)acrylate
copolymers, polyester- and/or polyurethane resins with
at least one a,~-unsaturated group bonded via the
carbonyl carbon atom of carbonyl, ester and/or amide
groups, with a C=C equivalent weight of 85 - 1800, and
a number average molecular weight (M~) of 170 - 10,000
g/mole, and with an OH number of up to 350 mg KOH/g,
wherein the weight percentages of components A and B are
each based on the solid and add up to 100 weight ~, and
C) 0.1 - 10 weight % of one or more thermally andtor
photochemically activatable initiators,
-: ~
D1) 0 - 20 weight % of one or more melamine resin
crosslinking agents,
D2) 0 - 40 weight ~ of one or more blocked --
polyisocyanates,
:: E) 0 - 40 weight ~ of one or more (meth)acrylol- ~:
functionalised reactive thinners which are free
from OH groups, ~.
::-
F) 0 - 30 weight ~ of one or more diols, triols,
~ ~polyols and~or hydroxyfunctional polyethers,
polyesters and/or (meth)acrylic copolymers
~` and optionally solvents, the usual lacquer
!`: additives, optionally water, optionally pigments
`~ and optionally extenders.
~ 35
~ It has been shown that a single-component coating medium such
~: as this is capable of storage. It is applied without a
~'~
.-:
.;~
:
-' 2102169
catalyst and a~ter application can be crosslinked or hardened
by heating to tempexatures of 100-180C. When photochemically
activatable radical initiators are contained, hardening may
be effected, by irradiation with W light for example, at the
same time as stoving or after stoving. The coatings obtained
withstand a more stringent acid test, namely treatment with
up to 40 ~ sulphuric acid at an elevated temperature up to
70C. The coatings obtained exhibit good hardness.
The crosslinking agents used as component A) in the coating
media according to the invention are preferably those which
contain at least two groups which are capable of alcoholysis
and which originate from one or more of the following
groupings, which may be the same or different:
W1 - CR - W2
~ 3
where R = alkyl and preferably H,
~ O O O ::
25 l~
W1 = -C-, -C-O-, C-N-, -P=O, -CN or NO2
O
. W2 = -C-O-alkyl
O O O ,':
W3 = _l_, -C-O~ -N-, -H, alkyl or alkyls,
':~
/~
;~ 40 wherein the alkyl and alkyls preferably comprise 1 to 6 C
atoms, and wherein the carboxyl or carbonamide groups defined
above for the W1, W2 and W3 radicals are each bonded to the CR
~; group via the carbon atom and the CR group is bonded to a
~`~ polymeric or oligomeric unit via at least one of the W1, W2
' `:
2102169
and/or W3 radicals. The functionality of component A) is on
average , 2 per molecule.
As stated above, the functionality of component A) is on
average , 2. This means that monofunctional molecules may
also be used in admixture with molecules of higher
functionality.
The crosslinking components A) described above contain at
least one ester group with Wz, which can crosslink with
compounds containing hydroxyl groups in the sense of an
alcoholysis reaction.
The crosslinking compounds are preferably substantially free
from primary, secondary or tertiary amino groups, since these
can have a negative effect on storage stability and light-
fastness.
Examples of crosslinking components A) which are capable of
alcoholysis and which correspond to the above general formula
are given below. These examples are subdivided below into
three groups: A1, A2, and A3.
In Group A1 the molecule contains an average of at least two
groups which are derived from methanetricarboxylic acid
monoamide units or acetoacetic acid ester-2-carboxylic acid
amides.
Examples of suitable A1 compounds comprise reaction products
of malonic acid diesters, 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 cycloaliphatic, aliphatic
or aromatic polyisocyanates such as tetramethylene
2102~6~
diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylene
diisocyanate, 1,12-dodecane diisocyanate, cyclohexanel,3- and
1,4-diisocyanates,l-isocyanato-3,3,5-trimethyl-5-isocyanato-
methylcyclohexane (= isophorone diisocyanate; IPDI), perhydro-
2,4~- and/or4,4'-diphenylmethane diisocyanate, phenylenel,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.
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 polyisocyanates containing carbodiimide groups,
allophanate groups, isocyanurate groups, urethane groups,
acylated urea groups and 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 with 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
~" 35 obtainable by the reaction of the above-mentioned simple
~`~ polyisocyanates, primarily diisocyanates, with
substoichiometric amounts of organic compounds with at least
:`
'
82102~69
- 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 ~nown prepolymers the ratio of isocyanate groups to
hydrogen atoms which are reactive towards NCO corresponds to
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.
-~ :
2~Q216~
Also suitable are the corresponding malonic esters of OH
group-containing acrylic resins, 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.
epoxide group-containing acrylate resins, glycidyl ethers of
polyols such as hexanediol, neopentyl glycol,
diphenylolpropane and -methane and hydantoins containing
glycidyl groups. Mixtures of these compounds are also
suitable.
The following examples of Group A2 illustrate a suitable
hardener component, which contains at least two groups
corresponding to formula (I)
~ ~
X '~: -
CR - K - (I)
Y
or structural units corresponding to formula (I')
X - CR - K (I')
~ Y
where:
~O 1OI
~ K = C or C - O,
and where the latter group is bonded via the C atom to the CR
- group;
Y = C - O - alkyl ~-
t~
2 1 ~C~ 169
and X =
R1 - C , CO2R1, CN, NO2, CONH2, CONHR1H, 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, . ~-
O O ' -
K' = C or C - O, .:
wherein the latter group is bonded to the CR group via the C
atom, and
O O
1~ 11
lS X' = C - O or C - N .
The number of groups (I) in the hardener according to the
invention is preferably 2 to 20, 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)
; 25 X ~
¦ CR - K ~ R2 tII)
Y ~ n
where X, Y and K have the meanings given above, R2 represents
a polyol radical .
: ~:
R2 ( OH ) n (K = C - O) ~- :
or the radical R2 of a polycarboxylic acid : - -~:~
.;; .::
~' ::
2~2~3 ~ :~
o
R2 (CO2H) n (K = (~
and n is at least 2, preferably 2 to 20, most preferably 2 to
10. 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 non-quantitative alcoholysis
of compounds of formula (III) or formula (IV)
RlO2C RlO2C
CR - K - Rl (III) --CR - K - Rl (IV)
Y R102C
with polyols R2(0H)n, where Y, K and R1 have the meanings given
above and the R1 radicals may be the same or different.
2 0 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,
di-~-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)phenyl)propane, 2-methyl-
1,3-propanediol, glycerine, trimethylolpropane, 1,2,6-
hexanetriol, 1,2,4-butanetriol, tris-(~-hydroxyethyl)-
isocyanurate, trimethylolethane, pentaerythritol and t!héir
hydroxyalkylation products, and also diethylene glycol,
triethylene glycol, tetraethylene glycol, polyethylene
~ glycols, dipropylene glycol, tripropylene glycol,
; polypropylene glycols, dibutylene glycol, polybutylene glycols
~`~ 35 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, ~-
2 ~ ~ 2 ~
hydroxydecanoic acid, ~-hydroxycaproic acid or thioglycollic ~ -
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.
s
Alternatively, the polyol may comprise an oligomeric or
polymeric polyol compound (polyol resin), the number average
molecular weight M~ 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 Mn 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/~. 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
2 1 ~ 2 1 ~ 9 ~ -
diisocyanate or isophorone diisocyanate, and biurets produced
from the reaction of three moles of a diisocyanate with one
mole of water, for example. Suitable polyurea polyols may be
obtained in a similar manner by the reaction of di- and
polyisocyanates with equimolar amounts of amino alcohols, 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.
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 OH group-containing polyacrylate polyols or
polyvinyl compounds 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.
~ 25 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, tetrachlorophthalic acids,
endomethylene tetrahydrophthalic acid and its hexachloro
" deri~ative, glutaric acid, maleic acid, fumaric acid, dimeric
and trimeric~ fatty acids such as oleic acid, optionally in
`:
`:
2102~ 69
14
admixture with monomeric fatty acids or cyclic monocarboxylic
acids such as benzoic acid, p-tert.-butyl benzoic acid or
hexahydrobenzoic acid, and also the reaction 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 component A2 which can be used
according to the invention comprises more or less viscous
liquids, or solids which are substantially soluble at least
in the usual lacguer solvents and which preferably contain
less than 5 weight ~, most preferably less than 1 weight ~,
of crosslinked constituents. The alcoholysis eguivalent
weight, which is a measure of the amount of groups (I) or
structural units (I') 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
between 500 and 5000 (determined by gel chromatography using
poIystyrene as the calibration standard). Methods of
preparing compounds such as these are described in detail in
EP-A-0 310 011. -
Additional examples of hardener components which can be used
~; according to the invention are those of Type A3, in which the
grouping capable of alcoholysis is derived from a compound -
containing a -Co-CRR3-CooR~ grouping, wherein R3 is a C1 - C8
alkyl or H, preferably hydrogen, and R4 = alkyl, such as '~
methyl, ethyl, butyl or t-butyl, for example.
: ~: :
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, OH-containing polymers,polyamines and polymercaptans. They are polyvalent with
respect to their alcoholysis function. They may be prepared,
for example, by the esterification of a polyepoxide with a -~
dicarboxylic acid monoester forming the grouping, e.g. malonic
--` 2102~9
acid monoester. An A3 component with one group capable of
alcoholysis for each epoxide group is obtained in this manner.
Aromatic or aliphatic polyepoxides may be used for this
purpose.
S
Further examples of suitable dicarboxylic acid monoethers
comprise malonic acid monoalkyl esters and acetone
dicarboxylic acid monoalkyl esters, wherein the alkyl radical
may be either straight-chain or branched with 1 to 6 C atoms,
e.g. methyl, ethyl, n-butyl or t-butyl.
:~'
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. Moreover, this
may optionally be assisted if the crosslinking components
~ 20 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.
.~
One or more (meth)acrylic copolymers or polyester- and/or
polyurethane resins are used as component B) in the vehicle
composition according to the invention. They contain at least --
one, preferably at least two, a,~-unsaturated groups bonded
;~ via the carbonyl carbon atom of carbonyl, ester and/or amide
groups as defined above. In addition, they contain OH groups
corresponding to an OH number of up to 350 mg KOH/g,
particularly at least one, preferably two, OH groups which can
react with the groups of component A) which are capable of
alcoholysis. The ~,~-unsaturated groups of component B) may
be incorporated in the chains of the copolymers or resins.
.
2~ 0216'~
16
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-OS- 16 16 79 and EP-OS- 22 41 58,
for example, to which reference is made here. These are B)
compounds with at least two groups corresponding to the
formula
RsR4c = CR4- Z (V)
in which:
Rs 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 -CO2Rl, a -CN, -NO2, -SO2-,
-CONHRl~ ^CONRlRl or -CORl group, wherein the Rls are the
~ same or different and are as defined above for formula
r ~ I; and --
represents -C-, -C - O or -C - N-
; ~ :. : :
!, : .. ::
wherein the two latter groups are bonded to the CR4 group
via the C atom.
Rs and R~ in the above RsR4-C group preferably each represent
` hydrogen.
The RsR4C = CR4 - Z group (V) may be derived from a mono- or ~ ~
multiply-unsaturated mono- or dicarboxylic acid with 2 to 20, ;
preferably 3 to 10, C atoms, for example.
:~
17 21021~9
Examples of carboxylic acids such as these include crotonic
acid and citraconic acid or their anhydrides, sorhic acid,
fumaric acid, mesaconic acid, substituted and unsubstituted
cinnamic acids, dihydrolevulinic acid, malonic acid
mononitrile, ~-cyanacrylic acid, alkylidene malonic acid,
alkylidene acetoacetic acid, and preferably acrylic acid,
methacrylic acid and/or maleic acid or their anhydrides. The
linkage to a polymeric carrier which is possible via the group
Z or also via the R4 radical may be effected via ester, amide,
urethane or urea groups.
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 oligomeric or polymeric.
The polyols concerned here are basically the same as those
listed in detail above in connection with component A), i.e.
polyhydric alcohols or oligomeric or polymeric polyol
compounds, e.g. polyether polyols, polyester polyols, acrylic
resin polyols and polyurethane polyols.
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
polyisocyanates such as hexamethylene diisocyanate ! with
~; hydroxyalkyl acrylates such 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,
~C
1~102~
polyester acrylates obtained by the esterification of
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. Component B) has an OH number less
than 350, most preferably from 20 to 200 mg KOH/g.
Like component A), component B) is preferably substantially
free from primary, secondary and tertiary amino groups.
The coating media used according to the invention contain 0.1
- 10 weight ~ of thermally and/or photochemically activatable
initiators, which form free radicals on decomposition, as
component C). The amount used is preferably 0.1 to 6 weight
~, based on the total amount of components A) and B).
~
The usual thermally activatable initiators which are familiar
to one skilled in the art may be used as thermally activatable
initiators, such as the usual peroxides, such as di-tert.-
butyl peroxide, tertiary butyl perbenzoate or tertiary butyl
peroctoate, for example; hydroperoxides, such as tertiary
~` butyl hydroperoxide or cumene hydroperoxide, for example; and
azo compounds, such as azo-bis-isobutyronitrile, for example.
However, initiators with labile carbon-carbon bonds are
` 35 preferred (so-called C-C initiators), such as benzpinacol
derivatives, e.g. benzpinacol, benzpinacol disilyl ether
210216~ ~
(monomeric or oligomeric), benzpinacol dimethyl ether, and
also tetraphenylethane and tetraphenylethane dinitrile.
The vehicle compositions according to the invention may also
contain the usual photo-initiators, such as those which are
known for radical and ionic polymerisation, as component C).
Suitable examples comprise initiators which absorb in the
wavelength region from 190 to 400 nm.
Examples of radical initiators which can be used include
chlorine-containing initiators such as chlorine-containing
aromatic compounds, e.g. those described in US-A-4 089 815;
aromatic ketones as described in US-A-4 318 791 and EP-A-0 161
463; hydroxyalkyl phenones as described in US-A-4 347 111;
water-soluble initiators, for example those based on
hydroxyalkyl phenones as described in US-A-4 602 097;
unsaturated initiators such as OH-functional aromatic
compounds, which may be esterified with acrylic acid, for
example, as described in US-A-3 929 490, EP-A-0 143 201 and
EP-A-0 341 560; or combinations of these types of initiators,
as described in US-A-4 017 652, for example.
Particular examples include 2-methyl-2-hydroxy-propiophenone,
benzophenone, thioxanthone derivatives, acylphosphine oxides
and Michler's ketone.
.
; Radical~ initiators which are most preferably used comprise
phosphine oxides and combinations of phosphine oxides with
other customary initiators, as described above.
` Examples of cationic initiators which can be used comprisetriarylsulphonium salts corresponding to the general formula:
(aryl) 3 S' X-
; 35
;~ wherein aryl represents an aryl radical such as the phenyl
~ radical, and X~ is an anion such as SbF6-, PF6-, AsF6- or BF4-,
- - ` 2 ~ 0 2 1 6 9
- as described in US-A-4 417 061, EP-A-0 327 194 and DE-A-2 904 -~
626. Other examples of cationic initiators include oxonium ~'
- salts, iodonium salts and diazonium salts, such as those
described in the following literature references; EP-A-0 161 -~
131, US-A-4 421 904, EP-A-0 145 633, EP-A-0 310 881, EP-A-0
310 882 (iodonium salts); DE-A-3 808 590 and DE-A-3 808 951
(diazonium salts). -~
:~:
In addition to these initiators, metallocene complexes, such
as those described in EP-A-0 094 915, for example, may also
be used. -~'
-. ,~,
The coating media according to the invention contain 0 to 20 - ~ -
weight ~ of one or more commercially available melamine resins '~
as component D1). These melamine resins may be etherified
with methanol, butanol or iso-butanol or mixtures thereof,
such as the commercial products Setamine VS 138, Maprenal MF
610, Cymel 254, Cymel 301 and Cymel 303, for example.
The coating media according to the invention may contain one
or more blocked polyisocyanates as crosslinking agents
(component D2). Examples of polyisocyanates which can be used
~ to form the basis of the blocked polyisocyanates include
~ cycloaliphatic, aliphatic or aromatic polyisocyanates such as ' '
tetra~methylene diisocyanate, hexamethylene diisocyanate,
2,~2,4-trimethyIene diisocyanate, 1,12-dodecane diisocyanate, ~'~
cyclohexane 1,3- and },4-diisocyanates, 1-isocyanato-3,3,5-
trimethyl-5-isocyanato-methylcyclohexane (= isophorone
diisocyanate; IPDI), perhydro-2,4'- and/or 4,4'-
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
J:
;!`'`~ ` 3,4-diisocyanato-4-methyl-diphenylmethane, naphthalene 1,5-
;~' diisocyanate, triphenylmethane 4,4'-triisocyanate,
~'~` 35 tetramethylxylylene diisocyanate or mixtures of these
compounds. ' ~ ~'
~;. :
210216~t~
21
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 polyisocyanates containing carbodiimide groups,
allophanate groups, isocyanurate groups, urethane groups,
acylated urea groups and 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 low molecular weight
polyisocyanates containing 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 with 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.
~; In these known prepolymers the ratio of isocyanate groups to
hydrogen atoms which are reactive towards NCO corresponds to
1.05 to 10:1, preferably 1.1 to 3:1, the hydrogen atoms
preferably originating from hydroxyl groups.
: ' . .
2~21~ ~
22
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 NC0 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.
The isocyanate groups of the polyisocyanates are completely
blocked. The usual blocking agents, such as those which are
used in the lacquer industry for example, may be used as
blocking agents. Examples of blocking agents which may be
used include malonic acid dimethyl ester, malonic acid diethyl
ester, acetoacetic acid ethyl ester, epsilon-caprolactam,
acetanilide, acetylacetone, acetonoxime, l,2-propanediol
and/or butanone oxime, the last-mentioned blocking agent being
preferred.
Blocking of the polyisocyanates may be effected, for example,
by heating one or more polyisocyanates with the blocking
agent. For example, one or more polyisocyanates may be
selected and heated with stirring, e.g. to about 80C,
whereupon the blocking agent is added (over about 10 minutes,
;~ for example). Stirring is continued until the NCO number is
~; less than 0.1 ~. It is also possible to block one or more
polyisocyanates with a mixture of two or more blocking agents.
The advantage of using two or more different polyisocyanates
and/or two or more different blocking agents is that this
; enables crosslinking to take place over a wide temperature
range.
"~ The coating media according to the invention may contain ~
unsaturated reactive thinners as component E) for adjusting
the viscosity. These are free from hydroxyl groups. They are
` 35 generally liquid at room temperature and are preferably of low ; ~-
viscosity.
` ~,' ~ .
~`` 2102169
Examples of reactive thinners such as these include
(meth)acrylates, such as lauryl (meth)acrylate for example;
alkyl glycol di(meth)acrylates such as ethylene glycol
di(meth)acrylate, diethylene glycol di(meth)acrylate,
propylene glycol di(meth)acrylate, tripropylene glycol
di(meth)acrylate; 1,6-hexamethylene di(meth)acrylate,
trimethylolpropane tri(meth)acrylate, triethylolpropane
triethoxy tri(meth)acrylate, pentaerythritol
tetra(meth)acrylate and ethoxylated andpropoxylatedvariants,
or 2-acetoacetoxyethyl (meth)acrylate.
The term "(meth)acrylate" is understood to mean acrylate
and/or methacrylate or acrylato- and/or methacrylato- in the
present description and in the claims.
The coating media according to the invention may contain
hydroxyfunctional compounds as component F). These are
selected, for example, from
a) polyols with at least two hydroxyl groups (i.e.
including diols, triols, etc.) from the group comprising
straight chain or branched alkanediols and polyols with
2 to 12 carbon atoms, or -
-'
b) hydroxyl group-containing poly(meth)acrylates or
poly(meth)acrylamides based on (meth)acrylic acid
hydroxyalkyl esters with 2 to 12 carbon atoms in the ~-
alkyl portion or (meth)acrylic acid hydroxyalkyl amides
with 2 to 12 carbon atoms in the alkyl portion,
optionally copolymerised with ~,~-unsaturated monomers,
with a number average molecular weight M~ of 1000 to
; 10,000 g/mole, or
c) polyester polyols or polyether polyols, each with a
number average molecular weight M~ of 500 to 2000 g/mole.
::
i '"`' : ` ~'.'. '. i""' ' ' .. ' '. .
21~2~9 ~
24
Examples of alkane di- and polyols of Group a) are those with
straight and branched chains with 2 to 12 carbon atoms. They
contain at least two hydroxyl functions, preferably at least
three, however. Examples of these include propanediol,
butanediol, hexanediol, glycerine, trimethylpropane ~nd
pentaerythritol.
Examples of hydroxyl group-containing poly(meth)acrylates b) -~-
comprise those based on (meth)acrylic acid hydroxyalkyl esters
of acrylic acid or methacrylic acid with alcohols with at
least two hydroxyl groups, such as 1,4-butanediol
mono(meth)acrylate, 1,6-hexanediol mono(meth)acrylate or
1,2,3-propanetriol mono(meth)acrylate. Examples of hydroxyl
group-containing poly(meth)acrylamides b) based on
lS (meth)acrylic acid hydroxyalkylamides include amides of
acrylic acid or methacrylic acid with hydroxyalkylamines or
di(hydroxyalkyl)amines, each-with 2 to 12 carbon atoms in the --
alkyl portion, and which may contain one or more hydroxyl
groups, such as acrylic acid hydroxyethylamide.
The hydroxyl group-containing poly(meth)acrylates of component
b) may be homopolymers or copolymers. They preferably have a
number average molecular weight of 1000 to 10,000, most
preferably from 3000 to 6000 g/mole. Copolymerisable monomers
for preparing the copolymers include a,~-unsaturated monomers,
radically polymerisable monomers from the group comprising
esters of a,~-unsaturated carboxylic acids such as acrylic
acid or methacrylic acid, examples of the alcohol component
comprising methyl, ethyl and propyl alcohols and their isomers
and higher homologues. Other examples comprise diesters of
maleic or fumaric acid, the alcohol component being the same -~
as that mentioned above. Further examples include vinyl
aromatic compounds such as styrene, a-methyl styrene and vinyl
toluene. Other examples include vinyl esters of short chain
`~ 35 carboxylic acids, such as vinyl acetate, vinyl propionate and
vinyl butyrate. It is also possible to use silane-modified
;~ monomers, such as gamma-methacryloxypropyl trimethoxy-silane
2102~6~
orgamma-methacryloxypropyl-tris-(2-methoxyethoxy-silane,for
example.
The coating medium according to the invention comprises a
mixture of components A, B, D, E and F and the radical
initiator C). The vehicles are compatible with each other and
may be mixed with solvents for better miscibility. Solvents
which do not subsequently have a negative effect in the
lacquer are preferred for this purpose.
Components A) to F) or mixtures thereof may be used in
solvent-containing form according to the invention. However,
it is also possible to produce aqueous coating media. The
components may be converted into an aqueous phase for this
purpose, optionally with low proportions of solvents and
optionally together with emulsifying agents. It is also
possible, of course, to use water-soluble components A to F.
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 components A to F in
the 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 the
components 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
2102~
26
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.
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 lower 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 -
70 weight %, for example, based on the final dispersion. Theymay optionally be diluted with water for 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 -Cl2 alkylphenol ethoxylates.
Solvent-based coating media preferably have a vehicle content
- of up to 70 weight %, most preferably up to 60 weight %. The
lower limit is preferably greater than 30 weight %, based on
the final coating medium in each case.
The coating medià according to the invention may be produced
from the individual components by the usual methods familiar
~ to one skilled in the art. For the production of the coating
i~ 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
~ .
21021~
27
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
literature. The usual pigments for primers, extenders, clear
or covering lacquers are suitable as pigments, for example
carbon black, titanium dioxide, finely dispersed silica,
aluminium silicate, French chalk, organic and inorganic
coloured pigments, transparent colorants, metallic pigments
or crosslinked polymer microparticles. Metallic lacquers,
coloured covering lacquers or clear lacquers may be produced
depending on the pigments and extenders selected.
The coating media according to the invention may contain
organic 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. xylene; 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; ethers, such
as methoxypropanol or butoxypropanol; or alcohols, such as
~ 25 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 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 constituents.
~ ;
The coating media according to the invention are single-
~ component systems. They are characterised by high storage
; stability and can be stored for more than six months without
~ ', ."", ~ , , , ", ,, ~
2~ l o 2 ~
significant changes in viscosity. Metallic substrates,
plastics, wood or substrates previously provided with coatings
are suitable as substrates.
The coating media according to the invention may be aqueous
or non-aqueous. In the aqueous system it is possible
optionally to incorporate the additives in the aqueous
dispersion of component A) or of component B). These
components may optionally be mixed before application to form
coating media. However, it is preferably also possible to
produce aqueous single-component systems.
The coating media produced in this manner may be applied in
the usual way, for example by spraying, immersion, by roller
or via a doctor blade. The covering lacquer coating is
applied to the substrate, which is optionally already provided
with further lacquer layers; After a venting-off phase (at
up to 80C) the applied coating medium is crosslinked by
heating. The stoving temperature is between 80 and 180C,
preferably between 110 and 150C. When the material contains
photochemically activatable initiators, hardening by
irradiation, using W light for example, may be effected at
the same time as or following stoving. The layer thickness
`~ of the stoved film is about I5 - 50 ~m. A hard, cross-linked,
glossy, acid-resisting lacquer coa~ing is produced in this
manner. One preferred embodiment is the application of the
coating medium according to the invention as a clear lacquer
coating on a base lacquer, preferably an aqueous base lacquer.
This opqration may be carried out wet-in-wet, or the base
lacquer may be previously dried by heating. This results in
particularly good bonding of the two layers. ~
. ~
:
Base lacquers which contain the usual covering lacquer
pigments may be over-coated with coating media formulated as
clear lacquers according to the invention, for example. The
base lacquers preferably contain special effect pigments, such
`:
~ ~t ~e ~
210216'~
28a
It is possible to heat the lacquer, e.g. to 60 to 100 C and to apply
it while hot. This reduces the viscosity of the lacquer and it can be
applied with a high solids content.
It is also possible to add super-critical carbon dioxide as a solvent
to the lacquer and to apply it in accordance with the so-called
Unicarb process, which, e.g. is described in EP-A 0 321 607 and in EP-
A 0 388 927.
t~ .~
. .,
i , .
,~ ,j ~ , ,
. .
. :~
.
. .
-
, .
~:
2102~9
29 -
as metallic pigments, for example. Polyester or polyuxethane-
or acrylic resins are preferably used as the basis of the
vehicle for the base lacquer. Binders such as these may
optionally be crosslinked via crosslinking agents, e.g.
melamine or isocyanate derivatives.
The coating media according to the invention are particularly
suitable for clear lacquers or covering lacquers; these are
preferably used in the motor vehicle industry, but may also
be used in other fields. The use of the coating medium
according to the invention in multilayer coatings is
particularly suitable for the coating of mass-produced
automobiles. However, it may be used for other purposes, such
as for domestic appliances for example, or in the furniture ;~
industry, in order to obtain coatings which are particularly
stable towards acids. --
: ~'":
The following examples serve to explain the invention. All
parts (pts.) and percentages (~) are given by weight.
Example 1
Preparation o~ a resin with groups capable of alcoholysis
(component A)
807 pts. of a commercially available polycaprolactonetriol
(CAPA305, Registered Trade Mark of Interox Chem. Ltd.) were
reacted at 80C in a reaction vessel with 700 pts. butyl
acetate, 350 pts. Solvesso 100 (a mixture of aromatic
hydrocarbons - Registered Tradei Mark) and 995 pts 3-
isocyanato-methyl-3,5,5-trimethyl-cyclohexylisocyanateuntil
an NCO content of 6.6 weight ~ was obtained. 637 pts.
acetoacetic acid ethyl ester were then added and the mixture
was maintained at 100C in the presence of 10 pts. zinc
acetylacetonate until an NC0 content of less than 0.1 weight
~ was obtained.
The resin had a viscosity of 1500 mPas (25C).
210216~
Example 2
Preparation of an acryloyl-functional resin (component B)
a) 1000 pts. xylene were placed in a 4 litre three-necked
flask fitted with a stirrer, thermometer, dropping
funnel and reflux condenser and heated to 90C with
stirring. A mixture of
380 pts. glycidyl methacrylate
128 pts. butyl methacrylate
252 pts. butyl acrylate ;~
200 pts. styrene and
40 pts. tert.-butyl peroctoate
was added drop-wise over 5 hours. The epoxy-functional
resin obtained had a viscosity of 70 mPas (25C) and a
solids content of 50.1 % (lh/150C).
b) 800 pts. of this resin were heated with stirring to 90C
in a two litre flask fitted with a stirrer, thermometer,
dropping funnel and reflux condenser. A mixture of 50
pts. acrylic acid and 1 pt. triphenyl phosphite was
added drop-wise at this temperature over 20 minutes, and
thereafter the reaction was allowed to proceed until an
acid number of 1 mg KOH/g was obtained. The mixture was
then concentrated under vacuum to give a solids content
of 60 weight %.
30 Exam~les 3a to 3f
Preparation of clear lacquer compositions
The following clear lac~uer compositions 3a to 3f were
prepared using components A and B as prepared in the two
Examples 1 and 2, respectively, and using a commercially -~-
' .:-' ' ~';~
..: : ~ .
: - ~: .'
2~021~)~
31
available oligomeric benzpinacol silyl ether as a radical
initiator (component C): ~ :
Clear lacquer1 (co~pone~t A) 2b (component B) 3 (component C)
3a 10 pts. 90 pts. 0 pts.
3b 10 pts. 90 pts. 3 pts.
3c 20 pts. 80 pts. 0 pts.
3d 20 pts. ao pts. 3 pt~.
3e 40 pts. 60 pt~. 0 pts. - ~
3f 40 pts. 60 pts. 3 pts. . .~ :.
The clear lacquers were applied using a doctor blade to glass -
plates to give a dry film thickness of 30 ~m and stoved for
20 minutes at 140C. The degree of crosslinking was
determined by measuring the pendulum hardness (Konig) before
and immediately after a ten-minute exposure to xylene and
after a 2-hour regeneration period. The comparative samples :~:
without a radical initiator exhibited significantly greater
softening under the effect of xylene than the samples with a
radical initiator according to the invention.
Pendulum hardne~s (~anig) in seconds
: Clear lacguer before xylene immediately after after a 2-hour
~: 25 treatmentxylene ~reatmentregeneration
period
3a 72 52 11
3b 183 79 121
3c 145 47 14
3d 196 156 166
3e 204 31 18
3f 218 190 199 :
` Example 4
Preparation of an aqueouQ clear lacquer
:~`
;: a) Components A, B and C were mixed as defined in Example ~ .
3 in the amounts according to Example 3f and
' ' ~: '
~ :4, ., ~
2~02~
concentrated under vacuum at a maxlmum temperature of
60C to give a solids content of 80 weight %.
b) 15S.2 pts. 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 about 8500 rpm. 388 pts. of the vehicle
mixture prepared as in 4a were added at 60C over 3
minutes. 50 pts. demineralised water were added. The
milky-white emulsion obtained had a solids content of
54.5 weight %.
c) Clear lacquer composition:
77.9 pts. of the emulsion from 4b
22.1 pts. demineralised water.
The aqueous clear lacquer had a solids content of 42.4 weight
%. It was applied using a spray-gun (1.3 mm nozzle) to give
a dry film thickness of about 50 ~m to blank sheet steel or
to a steel sheet provided with a multilayer coating comprising
electro-dip primer, extender and aqueous base lacquer, and was
stoved for 20 minutes at 140C after a 20-minute vent-off
phase (10 minutes at room temperature, 10 minutes at 80C).
The stoved film had a high hardness, good resistance to
solvents and a good appearance.
- ~
Properties:
on sheet steel Pendulum hardness: 170 s -~
MEK rub: >100
In built-up structure: Gloss (20C): 87
Pendulum hardness: 117 s
H2SO4 (100%, 65C): first slight --
effect visible ~
:
.. : . . .. .
21 0216~
33 :~
a f t e r 1 3
minutes
Cross-cutting
test: Characteristicvery good to good
: ,
,.- ~,..
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