Note: Descriptions are shown in the official language in which they were submitted.
8~35
~ PAT 85 068
L' 19.09.1985
BASf Farben + Fasern Aktiengesellschaft, Hamburg
Curable Composition
~ The invention relates to a curable composition
conta;n;ng a soluble hydroxyl-contain;ng acrylate copoly-
mer, a compound possessing at least two Cycl1c carboxylic
anhydride groups per molecule and a compound possess;ng at
least two epox;de groups per molecule.
Coating compositions which contain, as the essen-
tial b;nder, a hydroxyl-conta;n;ng acrylate copolymer are
well known. Aminoplast resins, for example alkylated
melamine/formaldehyde resins, are frequently used as cross-
link;ng agents for these hydroxyl-containing acrylate co~
polymers. Compositions o~ th;s type cure at temperatures
above 80C. In many cases, a strong acid, for example
p-toluenesulfon;c acid, ;s employed as a catalyst in these
systems.
For many intended uses, however, it is advanta-
geous if coating compos;tions cure at room temperature or
slightly elevated temperatures, for example in automotive
refinishing.
EP-E-64 338 discloses a hydroxyl-containing acry-
late copolymer which is cured with an aminoplast resin,
using a special catalyst mixture. This coating composi-
tion can be cured at room temperature but has the disadvan-
tage that the coatings based on th;s coating composition
have insufficlént resistance to water and steam.
`
; . ~., .. , ~, .,
-
- 2 - 3Lz~7889S
... ~ .
Systems which are based on epoxy/car-boxyl crosslinking and
cure at room temperature are also kn~wn. EP-A-123 793 published
November 7, 1984 describes compositions which cure at as low as
room temperature, consist of polyepoxides and polymers
S conta;ning carboxyl groups and tertiary amino groups, and
are obtainable by reacting vinyl polymers containing an~-
hydride and carboxyl groups with compounds which contain
at least one active hydrogen which is capable of reacting
with the anhydr;des and at least one tertiary amino group,
such as, for example, .ertiary amino alcohols. The compo-
sitions described have the advantage that they cure at as
low as room temperature and possess good resistance to
gasoline, ~ater and alkalis, and no undesirable discolor-
ation attributable to tertiary amino compounds occurs.
EP-A-134 691 published March 20, 1985 discloses curable
compositions which contain a compound having at least two hydroxyl
groups per molecule, a compound having at least two cyclic carboxy-
lic anhydride groups per molecule and a compound having
at least t~o epoxide groups per molecule. 30th conden-
sates and polymers are mentioned as suitable hydroxyl-
containing polymers. According to this patent appl;ca-
` tion, hydroxyl-contain;ng acrylate copolymers are mixed
with bis- and polycarboxylic anhydrides and bis- and poly-
epoxides, if appropriate with the concomitant use of a
catalyst, and the mixture is processed together ~ith sol-
vents and additives to give a coat;ng composition which
cures at as low as room temperature~
It is the object of lh~ ~resenr invention to im-
prove the properties of coatings based on epoxy/carboxyl
78~395
- 3 -
crosslinking from the point of v;ew of res;stance to
chem;cals, solvents, resistance to gasoline and resistance
to water and steam and from the point of view of flexib;-
lity and corrosion resistance. It is also desirable for
the coating composit;ons to cure, where appropriate, at
room~temperature so that they can be employed, for ex-
ample, in automotive refinishing.
This object is ach;eved, surpr;s;ngly, ;f an acry-
late copolymer hav;ng d h;gh content of copolvmerized poly-
ethylenically unsaturated monomers ;s employed as the hyd-
roxyl-conta;ning acrylate copolymer. Low viscosit;es
coupled w;th relat;vely h;gh sol;ds content can be ach;e-
ved by means of the acrylate copolymers employed ;n the
curable compos;'t;on; furthermore, as 3 result of the h;ghly
branched structure of the copolymers, high reactivity of
the hydroxyl groups toward the other funct;onal groups of
the curable compos;t;ons is ach;eved.
The ;nvent;on relates to the curable compos;t;on
of the type stated at the outset, where;n the hydroxyl-
conta;n;ng acrylate copolymer ;s obta;nable froma1) from 10 to 60% by we;ght, preferably from 15 to
60% by weight, of hydroxyl-contain;ng esters of acrylic
ac;d and/or methacryl;c ac;d, where the alkyl rad;cal is
of 2 to 14 carbon atoms,
a2) more than 3 to 30% by weight, preferably from 5 to
25X by weight, of monomers hav;ng at least two polymeriz-
able, olefinically unsaturated double bonds and
a3) from 15 to 82X by we;ght, preferably from 40 to
70X by we;ght, of further polymer;zable monomers hav;ng
~ ;~78~395
-- 4 --
an olefinicalLy unsaturated double bond,
the sum of components a1), a2) and a3) being 100~ by weight.
The'cho;ce of the further polymerizable monomers
of component a3 is not particularly cr;tical. They may
be selected from a group consist;ng of styrene, vinyltol-
uene; acryl;c ac;d, methacrylic acid, crotonic acid, ita-
conic ac;d, alkyl esters of acryl;c and methacryl;c acid,
alkoxyethyl acrylates and aryloxyethyl acrylates and the
.:
correspond;ng methacrylates, and esters of maleic and
fumaric acid. Examples are methyl acrylate, ethyl acry-
late, propyl acrylate, butyl acrylate, isopropyl acrylate,
isobutyl acrylate, pentyl acrylate, ;soamyl acrylate,
hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate,
3,5,5-tr;methylhexyl acrylate, decyl acrylate, dodecyl
acrylate, hexadecyl acrylate, octadecyl acrylate~ octa-
decenyl acrylate, pentyl methacrylate, isoamyl methacry-
late, hexyl methacrylate, 2-ethylbutyl methacrylate, octyl
methacrylate, 3,5,5-trimethylhexyl methacrylate, decyl
- methacrylate, dodecyl methacrylate, hexadecyL me'thacrylate,
octadecyl methacrylate, butoxyethyl acrylate, butoxyethyl
methacrylate, methyl methacrylate, ethyl methacrylate,
propyl methacrylate, ;sopropyl methaçrylate, butyl meth-
acrylate, cyclohexyl acrylate, cyclohexyl methacrylate,
acrylonitrile, methacrylon;tr;le, v;nyl acetate, v;nyl
chlor;de and phenoxyethyl acrylate. Other monomers can
be used prov;ded that they do not result in the copolymer
having undesirable properties. The cho;ce of component
a3 depends substant;ally on the des;red properties of the
curable composition ;n respect of flex;b;l;ty~ hardness,
~ 7889~
compatibility and polarity.
Among the compounds wh;ch can advantageously be
used as component a3 are from 0.1 to 20% by we;ght, pre-
ferably from 1 to 14~ by weight, based on the total weight
of alL monomers, of tertlary am;nes having a polymerizable,
S olefi~n;cally unsaturated double bond, for example N,N -d;-
methylaminoethyl methacrylate, N,N-diethylaminoethyl meth-
acrylate, 2-vinylpyridine, 4-vinylpyridine, vinylpyrro-
line, vinylquinoline, vinylisoquinoline, N,N -dimethyl-
aminoethyl vinyl ether and Z-methyl S-vinylpyridine. The
advantage of these tertiary amino groups ;ncorporated in
the acrylate copolymer is that they catalyze subsequent
carboxyl/epoxy crosslinking.
Compounds of the general formula
R O R
11 11
- CH2 = C - C - X - (CH2)n - X - C - C = CH
in which R denotes H or CH3, X denotes 0, NR , where
R is H or CH3, or S, and n denotes Z to 8, can advanta-
geously be used as component a2.
Examples of such compounds are hexanediol d;acry-
late, hexaned;ol dimethacrylate, glycol diacrylate, gly-
col dimethacrylate, butaned;ol diacrylate, butanediol di-
methacrylate, tr;methylolpropane tr;acrylate, tr;methylol-
propane tr;methacrylate and similar compounds. It is of
course also possible to employ comb;nat;ons of the poly-
unsaturated monomers. D;vinylbenzene may furthermore bementioned as a suitable component aZ.
It should be noted that, when, inter alia, tertiary
~ 78~395
- 6
am;nes possessing an olefin;cally unsaturated double bonr~
are used as component a3, d;- and polyesters of di- and
polyols w;th acrylic acid are not used as component a2,
since ;n th;s case gell;ng of the copolymer occurs.
S Component a2 may advantageously furthermore be a
react;on product of a carboxyl;c ac;d having a polymer-
;zable, olef;n;cally unsaturated double bond and glycidyl
acrylate and/or glyc;dyl methacrylate or a polycarboxyl;c
acid or monocarboxylic ac;d esterif;ed with an unsaturated
alcohol. If tert;ary am;no groups are ;ncorporated ;n the
acrylate copolymer, react;on products of a carboxyl;c ac;d
hav;ng an ethylenically unsaturated double bond, with the
exception of acrylic acid, w;th glyc;dyl methacrylate, or
w;th a polycarboxylic acid or unsaturated monocarboxyl;c
ac;d esterif;ed w;th an unsaturated alcohol, with the
exception of derivatives of acrylic acid, are suitable.
A reaction product of a polyisocyanate and an un-
saturated alcohol or am;ne can also advantageously be used
as component a2. The react;on product of one mole of
hexamethylene diisocyanate and two moles of allyl alcohol
may be ment;oned as an example of this.
Another advantageous component a2 is a d;ester of
polyethylene glycol and/or polypropylene glycol hav;ng a
mean molecular we;ght of less than 1500, preferably of
less than 10ûO, and acryl;c ac;d and/or methacryl;c ac;d.
In th;s case, where monomers possess;ng tert;ary am;no
groups are copolymer;zed, acryl;c ac;d der;vatives are
not used as component a2. Di- or polyvinyl compounds of
hydrocarbons, eg. div;nylbenzene, may also be used as
8~
: ~ 7
component a2.
Part;cularly suitable components a1 are hydroxy-
alkyl esters of acryl;c ac;d and/or methacryl;c acid poss-
essing a primary hydroxyl group, for example hydroxyethyl
acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate,
hydroxyamyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl
acrylate and the corresponding methacrylates.
At least some of the components a1 may advanta-
.
geously be a react;on product of one mole of hydroxyethyl
acrylate and/or hydroxyethyl methacrylate and on average2 moles of e-caprolactone.
Furthermore, component a1 can advantageously con-
s;st of up to 75~ by we;ght, part;cularly preferably up
to 50% by weight, based on the total amount of a1, of a
hydroxyl-containing ester of acrylic acid and/or methac~ry-
lic acid possess;ng a secondary hydroxyl group, in part;-
cular a react;on product of acrylic ac;d and/or methacry-
lic acid and the glyc;dyl ester of a carboxyl;c acid
possessing a tertiary a-carbon atom.
2-~lydroxypropyl acrylate, 2-hydroxybutyl acrylate,
3-hydroxybutyl acrylate and the correspond;ng methacry-
lates may be ment;oned as examples.
Advantageously used compounds hav;ng at least two
cyclic carboxylic anhydr;de groups per molecule are add-
ucts of tr;mell;t;c anhydride and a polyhydric alcohol.
Examples of suitable polyhydric alcohols are ethylene
glycol, propylene glycol, neopentyl glycol, hexane-1,6-
diol, glycerol and trimethylolpropane.
Other su;table polyanhydrides are benzophenone
'7~ 5
.
-- 8 --
tetracarboxylic dianhydrides of the general formula
.
O O
a
\ C/ ~ ~ \c / ' ' '
Il . ~
O O
where X is H, halogen, NOz-COOH or -S03H. 3,3',4,4'-aenzo-
phenonetetracarboxylic d;anhydr;de, 2-bromo-3,3',4,4'-
benzophenonetetracarboxyl;c d;anhydr;de and 5-n;tro-3,3'-
4,4'-benzophenonetetracarboxylic d;anhydride may be men-
t;oned as examples. Other su;table compounds having at
least two cyclic carboxyl;c anhydride groups per molecule
are cyclopentanetetracarboxylic dianhydride, phenoxyphenyl-
iO tetracarboxylic dianhydride, the tr;anhy~dride of benzene-
hexacarboxylic acid and of cyclohexanehexacarboxyl;c acid,
and 1,2,3,4-butanetetracarboxylic dianhydride. Preferably
used di- or polyanhydride compounds are copolymers o~
maleic anhydr;de w;th ethylen;cally unsaturated compounds.
Styrene and vinyl esters of organic acids may be mentioned
as examples of the latter.
Examples of compounds having at least two epoxide
groups per molecule are condensates of ep;chlorohydr;n
and b;sphenol A.
Cycloal;phat;c b;sepoxides of the formulae (I) and
(II)
O ~C - O - CHz O ~I)
.. i .
~L27~3~9S
_ 9 _
O O
O ~CHz - O - C - (CH2~4 - C - D - ~Hz~ o > O (~l~
.
R = H,CH3
are part;cularly preferred.
Other preferred di- or polyepoxide compounds are
. . . .
polyglyc;dyl esters and/or polyglyc;dyl ethers, such as
S ethylene glycol diglyc;dyl ester, glycerol polyglyc;dyl
ether, sorbitol polyglyc;dyl ether, tr;methylolpropane
polyglycidyl ether and pentaerythr;tol polyglyci~yl ether.
Epoxid;zed polybutad;enes, epoxide-contain;ng novolaks and
low molecular we;ght acrylate resins having oxirane side
groups, for example glyc;dyl methacrylate copolymers, are
also suitable.
The ;nvention furthermore relates to a process
for the preparat;on of a coat;ng composit;on based on the
curable composit;on accord;ng to cla;ms 1 - 21, where;n,
in order to prepare the hydroxyl-conta;n;ng acrylate co-
polymer
a1) from 10 to 60~ by we;ght, preferably from 15 to
6û% by we;ght, of hydroxyl-conta;n;ng esters of acrylic
acid and/or methacryl;c ac;d, where the alkyl rad;cal ;s
of two to 14 carbon atoms,
aZ) more than 3 to 30% by we;ght, preferably from 5
to 25% by we;ght, of monomers hav;ng at least two poly~
merizable, olef;n;cally unsaturated double bonds and
a3) from 15 to 80~ by weight, preferably from 40 to
. ...
8~395
- 10 -
70X by we;ght~ of ~further poLymerizable monomers having
an olefinically unsaturated double bond, the sum of com-
ponents a1, a2 and a3 being 100% by weight, are copo~y-
mer;zed ;n an organ;c soLvent at from 80 to 130rJC, preFer-
ably from 90 to 120C, using at least 0.5% by we;ght,
preferably 2.5~ by we;ght, based on the total we;ght of the
monomers, of a polymer;zation regulator and us;ng poLy-
merizat;on initiators, and the resulting acrylate soLution,
together with organic solvents, ;f appropriate pigments,
filLers, conventional ass;stants, add;tives, the compound
hav;ng at Least two cyclic carboxyl;c anhydr;de groups per
~ molecule, the compound having at Least two epoxide groups
- per molecule and, if appropriate, a crosslinking catalyst,
;s processed to a coat;ng composit;on by mix;ng and, ;f
requ;red, d;spers;ng. During the preparat;on of the ~
- acryLate copolymer, care should be taken to ensure that a
pre-crossL;nked but non-geLled copolymer is obtained. By
means of suitabLe polymer;zat;on cond;t;ons, it ;s poss-
;bLe, surpr;s;ngly, to prepare a clear, transparent, non-
gelled soLut;on of a branched copoLymer. The use of
monomers having at Least two ethyLen;caLly unsaturated
groups produces preliminary crossLink;ng of the copoLymer
moLecule, which, because of the special reaction condit;ons
according to the invent;on, nevertheLess does not result in
geLLed products. These speciaL reaction conditions com-
prise carrying out the poLymerization at temperatures of
80 to 130C, preferabLy 90 to 12ûC. The poLymerizat;on
;s advantageousLy carr;ed out so that a soLution of the
poLymer having a soL;ds content of from 40 to 65~ by
s
weight results. The cho;ce of ;nit;ator depends on the
amount of bifunct;onal monomers employed. Where this
amount ;s low, the ;nit;ators convent;onally used for such
temperatures, such as, for example, peroxy esters, can be
used~ For larger amounts of bifunctional monomer, in-
it;at~ors such as, for example, azo compounds are prefer-
ably employed. After the polymer;zation, the polymer
solut;on ;s concentrated to the des;red sol;ds contentr
preferably to solids contents of 60% by we;ght, by d;s-
t;ll;ng off the solvent. The clear copolymer solutionsthus obta;ned possess a viscos;ty of from 0.4 to 10 dPa.s
when adjusted to a solids content of 50~ by weight.
Particularly suitable polymer;zat;on regulators
are compounds conta;n;ng mercapto groups, preferably mer-
captoethanol. ~
If appropriate, catalysts for the epoxy/carboxylcrosslinking, for example tertiary amines, quaternary am-
monium compounds, and specific chromium and t;n compounds,
can, if appropriate, be employed ;n the process accord;ng
to the invention. Particularly preferably a tert;ary
amine, in an amount of from 0.5 to 10% by we;ght, based
on the weight o~ the epox;de component, ;s used as the
catalyst.
The use of an external c-atalyst is unnecessary in
most cases in which acrylate copolymers already conta;n
tertiary amino groups.
The curable compositions according to the inven-
tion can be m;xed with pigments, solvents and addit;ves
shortly before use.
~` - ,21~78895
The curable coating agents according to the inven-
tion can be applied onto a substrate in the form of a film
by spraying, flooding, dipping, roller coating, knife
coating or painting, the film then being cured to give a
firmly adhering coating.
The coatings according to the invention possess
improved properties in respect of resistance to gasoline
and resistance to water and steam, in comparison with the
coatings described in EP-A-134 691 published March 20, 1985
(see Example 1). With regard to resistance to solvents and
to chemicals, too, the coatings according to the invention
possess good properties.
The invention is illustrated in detail below with
reference to examples:
A) Preparation of copolymers according to the invention
(binder A)
In the examples below, all percentages are based on
weight and all parts are parts by weight, unless stated
otherwise. The solids contents were determined in a
through-circulation oven after 1 hour at 130C. The vis-
cosities were determined using a cone-and-plate viscometer.
Acrylate Resin I
The following are initially taken in a 3 ~ stainless
steel kettle and heated to 110C:
Initially taken mixture: 3~6.5 parts of xylene
193.2 parts of l-methoxyprop 2-yl
acetate
310.0 parts of a glycidyl ester of
a commercial a, a' -
,~1
~X788~5
- 13 -
dialkylalkanemonocarboxy-
l;c acid having the empiri-
- cal formula C13Hz403
(Cardura 10).
Feed 1 was metered ;n uniformly in the course of
3 hou~rs.
Feed 191 parts of acryl;c acid
86 parts of hydroxyethyl methacrylate
. . .
219 parts of styrene
10 150 parts of butanediol dimethacrylate
144 parts of methyl methacrylate
40 parts of mercaptoethanol
Feed 2 is metered ;n uniformly in the course of
3.5 hours. The two feeds are begun simultaneously.
15 Feed 232 parts of azobisisobutyron;tr;le
328.2 parts of xylene
164~1 parts of 1-methoxyprop-2-yl
acetate
The temperature ;s kept at 110C during the polymer;-
zation, after wh;ch it is kept at 130~C for 3.5 hours.
Thereafter, 380 parts of solvent mixture are d;st;lled off
at 100C and under 180 mbar.
The acrylate res;n solut;on thus obta;ned has a
sol;ds content of 58.7~, a v;scosity of 14.5 dPa.s and an
Z5 ac;d number of 14.5.
Acrylate resin II
The follow;ng are ;n;t;ally taken ;n a 3 l stain-
less steel kettle and heated to 110C:
In;t;ally taken m;xture: 424.8 parts of xylene
- ...
. .
~27~3~395
. .,
- 14 -
212.4 parts of 1-methoxyprop-2-yl
acetate
310.0 parts of a glyc;dyl ester of
a commercial a -d;alkylal-
kanemonocarboxylic acid hav;ng
the empir;cal formula C~3H2403
(Cardura E 10)
Feed 1 ;s metered ;n un;formly in the course of
- .
3 hours.
10 Feed 1 91 parts of acrylic acid
161 parts of hydroxyethyl methacrylate
219 parts of styrene
150 parts of butanediol dime~hacrylate
69 parts of methyl methacrylate
5 - 40 parts of mercaptoethanol
Feed 2 is metered in uniformly in the course of
3.5 hours. The two feeds are metered ;n simuitaneously.
Feed 2 28 parts of azob;sisobutyronitrile
287.2 parts of xylene
143.6 parts of 1-methoxyprop-2-yl
acetate
The temperature is kept at 110-112C during the
polymerization after wh;ch the solution ;s kept at 130C
for 4 hours. 428 parts of solvent m;xture are dist;lled
off at 100C and under 180 mbar. The acrylate resin
solution thus obta;ned has a solids content of 61.4% (15
m;nutes 180C) a viscosity of 38.5 dPa.s and an ac;d
number of 13.6.
'
1~7~3895
- - 15 -
.
Acrylate resin IlI
The following are initiaLly taken in a 3 l stain-
less steel kettle:
Initially taken mixture: 107.3 parts of xylene
214.6 parts of 98/100 butyl
acetate
The initially taken mixture is heated to 110C.
The follow;ng are metered in uniformly in the course of
- .; . , .
3 hours:
10 Feed 1: 140 parts of styrene
119 parts of n-butyl acrylate
70 parts of tert-butyl acrylate
140 parts of butaned;ol d;methacrylate
70 parts of hydroxyethyl methacrylate
31.5 parts of mercaptoethanol
Feed 2: 21 parts of 4-vinylpyrid;ne
20 parts of xylene
20 parts of butyl acetate
The following ;s metered ;n un;formly in the
course of 4 hours:
Feed 3: 25~2 parts of azobis;sobutyronitrile
131.6 parts of xylene
263.2 parts of 98/100 butyl acetate
The feeds are begun simultaneously; the tempera-
ture ;s kept at 110C dur;ng the polymer;zat;on and,
when feed 3 ;s complete, polymer;zat;on ;s cont;nued for
3 hours at 110C. The acrylate res;n solut;on obta;ned
has a sol;ds content of 48.7%, a v;scosity of 1.4 dPa.s
and an acid number of 1.3.
_~ - 16 - ~ ~788g~
PreparatiOn and testiny of c~ear coats containing the
acrylate resin solutions I - III
Coating formulat;on 1
2.90 parts of a bisanhydride ootained from tri-
mellitic anhydride and 1,2-ethanediol
7.80 parts of methyl ethyl ketone and
3.5Z parts of 3,4-epoxycyclohexylmethyl 3,4-epoxy-
cyclohexanecarboxylate
are mixed.
10.00 parts of the acrylate resin from Example I
and
0.28 part of a metal salt catalyst solut;on
(accelerator Cordova AMC-2)
are added to this solution.
Coating formulation 2
2.9 parts of a b;sanhydride obta;ned from 2 moles
of trimellitic anhydride and 1 mole of 1,2-ethanediol,
7.10 parts of methyl ethyl ketone and
3.5Z parts of bis-(3,4-epoxycyclohexyl) adipate
are mixed with one another.
10.00 parts of the acrylate res;n from Example II
and
0.40 part of a metal salt catalyst solution (acce-
lerator CORDOVA AMC-2).
are added to this solut;on.
Coating formulat;on 3
2.90 parts of a bisanhydr;de obta;ned from Z moles
of trimell;t;c anhydride and 1 mole of 1,2-ethanediol,
7.20 parts of methyl ethyl ketone and
* Trade mark.
88~5
- 17
3.52 parts of 3,4-epoxycyclohexyl 3,4-epoxycyclo-
hexanecarboxylate
are mixed with one another.
11.5 parts of the acrylate resin from Example III
are added to this solut;on.
. Immed;ately after mix;ng, 200 ~m f;lms of the
coatings are applied onto glass panels, and, after drying
for 16 hours at room temperature, the films are tested
r w;th regard to hardness, resistance to gasoline and res;s-
; 10 tance to water.
The pendulum hardness is determined by the Konig
method, in the gasoline test a felt pad impregnated with
FAM mineral spirit is covered and le-ft on the film for 1
hour~ and in the water test a large drop of water (dia-
meter 5 cm) is left on the film for~ 2 hours.
Coating film Pendulum hard- Resistance Resistance
from Example ness tKonig) to gasoline to water
1 63'' no softening no softening
no marking no ~arking
20 ~ 45'' no softening no softening
no marking no marking
3 91'' no softening no softening
no mark;ng no mark;ng
