Note: Descriptions are shown in the official language in which they were submitted.
3-1~288/-~
Curable composi-tion based on an acid-curable resin9 and
Err cess for c _in~_this resin _ __
The invention relates to compositions based on an
acid-curable resin and containing a blocked curing cata-
lyst, and to a process for curing this resin by irradia-
tion with short-wave light and subsequen-t heating.
Acid-curable resins are used especially as binders
for finishes, printing inks and paints, when high baking
temperatures are to be avoided. The acid-curable
resins can be amino resins, including etherified, esteri-
fied or otherwise modified melamine resins, urea/form-
aldehyde resins, phenol/formaldehyde resins as well as
mixtures of such resins with alkyd resins, polyester
resins or acrylic resins. Further acid-curable resins
are me-thylol compounds, methylol ethers of polycarboxylic
acid amides, for example deriva-tives of polyacrylic or
polymethacrylic acid, urethane-alkyds as well as resins
which contain carboxylic acid esters of N-methylol~amides.
Acid-polymerisable or acid-curable ethylenically unsatur-
ated materials, such as N-methylol-acrylamide, vinyl
carbazole, vinyl ethers9 diketene and diacetone-acrylamide
can also be usedO The acid curing catalysts used are
predominantly organic acids, such as sulfonic acids9 in
particular p-toluenesulfonic acid, half-esters ox phthalic
acid or maleic acid, or phosphoric acid and its partial
esters. Since these acids effec-t slow curing even at
room temperature, they are added to the resin only shor-tly
before -the lat-ter is applied, and -this leads to the
.
I
5~
known problems in main-taining defined po-t lives. To
make one-componen-t sys-tems feasible, i-t has already been
proposed to use blocked curing catalysts, from which -the
acid is libera-ted a-t an eleva-ted tempera-ture. Ex-
amples of such catalysts are amine salts of the acids,
for example the pyridine sal-ts of aromatic sulfonic acids,
as proposed in U.S. Patent Specification 3947L~,05L~.
These and other salts have the disadvantage that
they either already effect slow curing during s-torage or
-that they require very high curing temperatures or very
long curing -times. Moreover 5 they cause odour problems.
Furthermore, U.S. Patent Specification 4,102,687
has proposed the use of aromatic sulfonium salts of com-
plex anions, for example of BF4, PF`6, SbF6 or AsF6, as
blocked curing catalys-ts, from which the actual curing
catalyst is formed by irradia-tion with W light.
According to German Offenlegungsschrift 2,602,57L~, the
same principle can also be realised with aromatic iodonium
salts. However, it is difficult to prepare sulfonium
salts or iodonium salts of this type in a pure form, and
they have a low reactivity and tend to cause yellowing of
the resins. There is therefore a need for compounds
which can readily be prepared on an industrial scale and
which, on irradiation with short-wave ligh-t, rapidly
decompose -to form a highly reactive curing catalyst for
acid-curable resins.
It has now been found tha-t sulfonic acid es-ters
of certain cyclic hydroxamic acid deriva-tives 9 which can
readily be prepared industrially, meet these requirements,
since they have unlimited storage life in -the dark but, on
exposure to short-wave ligh-t 9 rapidly decompose -to form
sulfonic acids which make a subsequen-t acid-ca-talysed
curing of the resins possible a-t a relatively low temp-
erature and do not tend to cause yellowing of the resins.
The invention relates to a curable composition,
comprising an acid-curable resin and, as a blocked curing
catalyst, a compound of the formula I or II
5~
-- 3 --
0
/ \ / 2 ~.1-0-SC
O R R"
I II
in which R is Cl-C18-alkyl, phenyl which is unsubstituted
or substituted by Cl-C12-alkyl, halogen, Cl-C4-alkyl-
NHCO-, phenyl-NHCO-, N02 or Cl-C4-alkoxy9 or is naphthyl
which is unsubstituted or substituted by Cl-C12-alkyl or
halogen, or is C5-C6-cycloalkyl, camp4horyl, CF3, CC13,
CH2Cl, F or NH2 and R , R , R and R independently of one
another are hydrogen, Cl-C8-alkyl, Cl C4-alkoxy, Cl-C12-
alkyl-thio, phenyl-thio, N02 or halogen.
Preferably, the curing ca-talyst is a compound of
the formula I or II, in which R is Cl-C18~alkyl, F9 CF3,
CC13, or phenyl or naphthyl which are unsubst~tu-ted or
substituted by C~-C12-alkyl, Cl or CH3CONH, or is cam-
phoryl and R , R , R3 and R independently of one another
are hydrogen, Cl-C4-alkyl, Cl-C4-alkoxy or Cl-C4-alkylthio.
The compounds of the formula I are derivatives of
N-hydroxy-phthalimide, and the compounds of the formula II
are derivatives of N-hydroxy-naph-thalimide. They can
be prepared from the corresponding N-hydroxyphthalimides
or N-hydroxynaphthalimides by esterification with the
corresponding sulfonic acids or -the acid chlorides or
anhydrides thereof, according to the methods known for
such compounds, as they are described in Annalen 616~
183 (1958) and in Journal of Organic Chemistry 20, 33
(1955) and 38, 3908 (1973).
The following are examples of individual compounds
of the formula I- N-phenylsulfonyloxy-phthalimide, N-p-
tolylsulfonyloxy-phthalimide, N-methylsulfonyloxy-phthal-
imide, N-hexadecylsulfonyloxy-phthalimide, N -trifluoro-
methylsulfonyloxy-phthalimide, N-fluorosulfonyloxy-
phthalimide, N-chloromethylsulfonyloxy-ph~thalimide,
54
-- 4 --
N-trichlorome-thylsulfonyloxy-ph~thalimide, N-bu-tylsulfonyl-
oxy-ph-thalimide, N-dodecylsul:Eonyloxy-ph-thalimide, N-
naphthylsulfonyloxy-phthalimide, N-2,4,5--trichlorophenyl-
sulfonyloxy-phthalimide, N-2,4,6-trime-thylphenylsulfonyl-
oxy-phthalimide, N-2,~-i,6-triisopropylphenylsulfonyloxy-
phthalimide, N-cyclohexylsulfonyloxy-ph-thalimide, N-4-
nitrophenylsulfonyloxy-ph-thalimide, N-4-chlorophenyl-
sulfonyloxy-phthalimide, N-4-acetylaminophenylsulfonyloxy-
phthalimide, N-4-methoxyphenylsulfonyloxy-phthalimide, N-
p-tolylsulfonyloxy-3-nitro-phthalimide, N-methylsulfonyl-
oxy-3-nitro-phthalimide, N p-tolylsulfonyloxy-4-nitro-
phthalimide, N-p-tolylsulfonyloxy-4-methyl-ph-thalimide,
N-p--tolylsulfonyloxy-3-ethylthio-phthalimide and N-phenyl-
sulfonyloxy-4-chloro-phthalimide.
The following are examples of individual compounds
of the formula II: N-p-tolylsulfonyloxy-naphthalimide,
N-me-thylsulfonyloxy-naph-thalimide, N-dodecylsulfonyloxy-
naphthalimide~ N-butylsulfonyloxy-naphthalimide, N-tri-
fluoromethylsulfonyloxy-naphthal.imide, N-fluorosulfonyl-
oxy-naphthalimide, N-nonylnaph-thylsulfonyloxy-naphthal-
imide, N-p-dodecylphenylsulfonyloxy-naphthalimide, N-
phenylsulfonyl.oxy-naph-thalimide, N-camphor-10-sulfonyloxy-
naphthalimide, N-trichlorophenylsulfonyloxy-naphthalimide 9
N-2,4,6-triisopropylsulfonyloxy naphthalimide, N-ethyl-
sulfonyloxy-naph-thalimide, N-p-chlorosulfonyloxy-naphthal-
imide and N-xylylsulfonyloxy-naphthalimide.
The curing catalysts according to the lnvention
are added to the resins in a quantity which is sufficient
for curing. The required quantity depends not only on
the type of resin but also on the intended curing -tempera-
ture and curing time. In general, 0.1 to 10% by weight 9
preferably 0.5 to 5% by weight, relative -to -the solvent-
free resin, are used.
All those resins can be used, the curing of which
can be accelerated by acid catalys-ts. These are
especially surface-coa-ting resins based on acrylic resins,
polyester resins, alkyd resins, melamine resins urea
-- 5 --
resins and phenolic resins, and in particular mixtures of
acrylic resins, polyester resins or alkyd resins wi-th one
another or wi-th a melamine resin. These also include
modified surface-coating resins, for example acrylic-
modified polyes-ter or alkyd resins. Examples of
individual -types of resins which fall within -the scope of
the term acrylic, polyes-ter and alkyd resins, are des-
cribed in Wagner, Sarx '~Lackkuns-tharze (Synthe-tic Resins
for Finishes)" (Munich 7 1971), pages 86 -to 123 and 229 -to
238, or in Ullmann "Encyclopadie der techn. Chemie
(Encyclopaedia of Industrial Chemistry)", 4-th edition,
volume 15 (1978), pages 613 -to 628. acid catalysis
is of particular importance for the curing of finishes
which contain etherified amino resins, for example me-thyl-
a-ted or butylated melamine resins (N-methoxymethyl- or
N-butoxymethyl-melamine respec-tively) or me-thylated/
bu-tylated glycol-urils
o
for example CH30C~l2- -clloCH
C~13C112~N~\ ~N~C~12ocH3
11
o
and the ]iker
For cer-tain purposes, resin compositions are also
used which contain monomeric or oligomeric consti-tuents
having unsaturated groups capable of polymerisa-tion.
Resin compositions of this -type can also be cured by the
process according -to the inven-tion. In this case,
free-radical polymerisation initiators or photo-initiators
can also be used addi-tionally. The former initiate
the polymerisa-tion of the unsa-tura-ted groups during the
heat treatment, and the latter initia-te the polymerisation
during the W irradia-tion. Resin compositions of this
type, having ~msaturated components, can also be
-- 6 --
polymerised by elec-tron beams. However, acid-
ca-talysed crosslinking mus-t always -take place in addi-tion
to the polymerisa-tion of the unsatura-ted componen-ts.
The finishes can be solutions or dispersions of
the surface-coa-ting resin in an organic solven-t or in
wa-ter, or they can be solvent-free. Finishes wi-th a
small proportion of solven-t, so-called "high solids
finishes", are ox par-ticular interest. The finishes
can be clear finishes, such as are used in
the motor vehicle industry as topcoats of multi-coat
paints. They can also contain pigments which may be
inorganic or organic pigments, as well as metal pigments
for metallic-effect finishes.
Moreover,the finishes can contain minor amounts of
special additives conventional in surface coa-ting -tech-
nology, for example flow control agents, thixo-tropic
agen-ts, light-s-tabilisers or antioxidan-ts.
Examples of light-stabilisers are -those from the
group comprisirg hydroxyphenyl-benzotriazoles, hydroxybenzo-
phenones, cyanoacrylates, hydroxyphenyl-triazines, oxal-
anilides,organic nickel compounds and polyalkylpiperidine
derivatives. Since light-stabilisers of the W
absorber type can interfere with the Us irradiation
according to the invention, ligh-t-stabilisers of this
type can also be added to an adjacen-t coat, from which
they -then gradually diffuse into that layer of the baking
finish which is -to be stabilised. The adjacent coat can
be a primer underneath the baking finish or a topcoat
above the baking finish.
As an alternative, it is also possible to circum-
vent the interfering influence of a W absorber by the use
of so-called "blocked W absorbers", such as are
described in German Of:Eenlegungsschrif-t 2,648,367.
Products which form a W absorber by a Fries photo
rearrangemen-t, for example resorcinol monobenzoa-te, are
also sui-table.
Polymethylpiperidine derivatives or combina-tions
~gs~
thereof with blocked) W -absorbers are preferred.
The following composi-tions according -to the
inven-tion represen-t further special preferred embodimen-ts
of the invention:
a) A composi-tion which, as -the resin, con-tains an
amino resin or a mixture of an amino resin with another
resin, or a resin con-taining methyl-amino groups.
b) A composition which, as the acid-curable resin,
contains a phenolic resin or a phenol/formaldehyde resin,
or a mix-ture of such a resin with another acid-curable
resin
c) A composition which, as the base resin, contains
a mixture of acryla-tes and melamine resins (hybrid sys-
tems) and in addition, if appropriate, free-radical
polymerisation initiators or photo-initia-tors.
d) A composition which, as the acid-curable resin,
contains the following mixture:
hexamethoxymethylmelamine 17.93 parts by weight
butyl aceta-te 9.73 parts by weight
cellulose acetobutyrate 1.83 parts by weight
a silicone resin in
organic solvents 2.80 parts by weight
a flow control agent
based on a polymer 0.29 part by weight
an acrylic resin having
functional hydroxyl groups 57.30 parts by weight
n-butanol 10.12 parts by weight
100.00 parts by weight
e) A composi-tion which, in addition to the resin and
the curing catalyst1 also contains further additives con-
ventional in resin technology.
f) A composition which additionally contains one or
more ethylenically unsaturated compounds.
g) A composition according to f), which additionally
contains a photo-initiator from the aromatic ketone
series.
h) A composition which, as -the curing catalyst,
contains a compound of -the formula
o
> 2
o
in which R is-~CH3~ -C4Hg~ -C12H25' -C16H~3 or
12 25 \ /and preferably is -~4Hg or -C12H25.
i) A composition which additionally contains 0.1-5%
by weigh-t of a monohydric or polyhydric aroma-tic alcohol.
j) A composltlon according to i) which, as -the
aromatic alcohol, contains hydroquinone, 2,6-di--tert.-
butyl-4-me-thylphenol or bisphenol A.
k) A composition which additionally contains 0.1-2%
by weight of phenanthrenequinone.
The inven-tion also rela-tes to a process for curing
acid-curable resins in the presence of curing ca-talysts of
the formula I or II by irradiation wi-th short-wave light
and subsequent heating.
The irradiation of -the resin wi-th short-wave
ligh-t is preferably carried out wi-th W ligh-t9 a number
of sui-table industrial devices being available nowadays
for this purpose. These include medium-pressure,
high-pressure or low-pressure mercury lamps as well as
fluorescent tubes, the emission maxima of which lie at
250 to Loo nm. The required irradiation times depend
on the layer thickness of the resin, on the pigmen-tation,
on the ligh-t intensity of the lamps and on the dis-tance
of the lampsi An unpigmented finish in the usual
layer thickness requires a few seconds of exposure time
in conventional W irradiation devicesO During this
time, the latent catalys-t is photochemically converted to
form a free sulfonic acidO
If pho-to~sensitisers are added -to the resin, the
5~7
g
irradlation can also be carried ou-t wi-th daylight lamps.
Examples of known photo-sensitisers are fused aromatics,
:for example perylene, aroma-tic amines (such as are
described in U.S. Paten-t Specification
4,069,054) or cationic and basic dyes (for example
-those described in U.S. Pa-tent Specifica-tion
4,026,705).
Since the acid-curing proceeds very slowly at
room temperature, it is necessary for an industrial
application of the process to follow -the irradiation
wi-th a heat treatment. In contrast to other processes
using curing catalysts which can be split by heat, how
ever, this treatment can be carried out at rela-tively low
temperatures. With a baking time of abou-t 30 minutes
and the use of about 2% of catalyst, temperatures of 70
to 80C are sufficient. When 1% of ca-talyst is used,
temperatures of 80 to 100C are required and, when 0.5%
of catalyst is used, temperatures of abou-t 100 to 120C
are required. Preferably, the resins catalysed in
accordance with the invention are cured, after irradiation,
at temperatures below 130C. By contrast, even bak-
ing -temperatures of more than 130C are required in some
cases for the curlng with known amine salts of sulfonic
acids (without irradiation).
These relatively low baking temperatures of the
process according to -the inven-tion are of considerable
industrial importance in the coating and pain-ting of
-temperature-sensitive substrates, for example ar-ticles of
wood or cardboard, and in particular articles which con-
tain components of plastics or rubbers, for example
electrical appliances, vehicles of any type or machines
A further advantage over other one-component
resins containing a curing catalyst is that the one-
component systems according -to -the invention have a
vir-tually unlimited storage life at room tempera-ture,
since the active catalyst is formed only during the
irradiation.
~Z~4~
-- 10 --
The process according to -the invention is suit-
able for all -types of indus-trial coa-ting and painting,
for example for painting machines, vehicles, ships or
s-tructural componen-ts. I-t is of particular import-
ance for mo-tor vehicle pain-ting. In this case, it
can be used in a single-coa-t paint or in a mul-ti-coa-t
paint. The use of the process for -the con-tinuous
coating of sheet me-tal, for example s-teel sheet or
aluminium sheet, by the so-called coil-coat process is
also of particular in-terest. Additionally, the pro-
cess is suitable for the curing of acid-curable printing
inks which, because of their excellent stability in deep-
drawing, are par-ticularly suitable for -the printing of
shee-t metal.
When the process according -to the invention is
used with compression-moulding compounds, casting resins
and laminating resins, -the resins can first be irradiated
in a thin layer and then be hot-formed and cured to give
any desired articles. However, if these are articles
of relatively small thickness, -the resins can also be
shaped first and subsequently irradia-ted and heated.
In -the irradiation of the resins, the layer -thickness can
be several millimetres, depending on their transparency.
A further possible application of the process is in the
prepara-tion of relief forms, for example printing plates.
In -this case, the solid or liquid acid-curable resin
composition which can also contain unsaturated monomers/
prepolymers as well as photo-initiators or polymerisation
initiators, is first exposed through a negative :Eilm.
Subsequently, if appropria-te, a thermal after-trea-tment
is carried out, the exposed areas being crosslinked.
Finally, -the printing plate is developed by washing out
the uncrosslinked areas. Printing plates for letter-
press printing, flexographic printing or offset printing
can be prepared correspondingly.
The examples which follow explain the process in
more de-tail by reference to specific compositions
5~
-- 11
according -to -the inven-cion. In -the examples, -the
parts and percentages are by weight. The -tempera-tures
are given in degrees C.
Example 1: Curing of a finish based on an acrylic/
melamine resin.
0.5 mm thick aluminium sheets which had been
coated with a whi-te-pigmented primer based on polyes-ter
resin, are coated with a high-solids clear finish of -the
following composition:
53.7 parts of acrylic resin (Paraloid OL 42, Rohm & Haas
Co., USA)
19.3 par-ts of melamine resin (Cymel 301, Amer. Cyanamide
Co. )
1.9 parts of cellulose acetobutyrate (CAB 551, Eastman
Chem. Co.)
10.6 par-ts of n-butanol
10.5 parts of butyl acetate
3.0 parts of flow control agent (Byketol Spezial, Byk-
Mallinckrodt)
0.4 part of flow control agen-t (Modaflow, Monsanto Comp.)
o.6 part of curing ca-talyst.
The catalyst is first dissolved in a part of the
butanol. The finish has a solids content of 62.1%
(binder). The catalyst quan-tity therefore corresponds
to 1% 9 relative to solvent-free binder.
The finish is applied with an electric film
spreader in such a way that the dry film thickness is
about 30 em. After an air-drying time of 15 minu-tes,
the samples are exposed, in a PPG irradiation apparatus
with 2 high-pressure mercury vapour lamps of 80 Wa-t-t
each, to W irradiation, the irradiation period being
varied. Subsequently, the samples are baked for 30
minu-tes a-t 100C in an oven.
To assess the degree of curing, the pendulum hard-
ness of -the finish film is determined by the method
according -to K8nig (DIM 53,1573, and this is done 30
minutes after baking.
4sg~
To assess -the discolora-tion (yellowing), the
colour difference QE according to DIN 6,174 is de-termined.
The results are listed in Table 1.
Table 1
.
Catalyst Irradiation Pendulum Colour
time hardness difference
(seconds) (seconds) YE
. ...
N-Methylsulfonyl-
oxy-phthalimide 2.1 102 1.9
4.2 113 3.0
12.6 120 5.2
25.2 120 6.4
N-Phenylsulfonyl-
oxy-phthalimide 2.1 69 1.1
4.2 83 1.5
12.6 86 2.6
25.2 87 3.8
. I. .
N-p-Tolylsulfonyl-
oxy-phthalimide 2.1 81 1.4
4.2 95 2.0
12.6 106 3.6
25.2 106 5.0
. _ . __ _ . .
Addi-tionally, the s-torage stability of the finish
samples is checked by measuring the viscosity during
storage at 60C for 7 days, using the ICI cone-and-plate
viscometer.
In this method, the viscosi-ty is measured in
poise. The difference between this viscosi-ty (I
and the viscosity of a catalyst-free finish sample is
indicated in Table 2.
Table 2
_ . _ . I,
Catalysts Viscosity difference A in poise
after s-torage for
0 1 2 3 4 7atday600c
... . . .. _ ... . ._ _ _ _
N-Me-thylsulfonyloxy-
phthalimide 0.5 1.3 2.3 2.3 3.2 2.9
N-Phenylsulfonyloxy-
phthalimide 0 0.4 0.6 o.6 0.5 0.4
N-p~Tolylsulfonyloxy-
phthalimide 0 002 0.7 0.7 0.4 0.5
~,f.~5
-- 13 --
Example 2:
The compounds listed in Table 3 below are incor-
porated as catalysts in-to the high-solids clear finish
described in Example 1 (amoun-t of ca-talyst: o.6 par-t).
Testing is carried ou-t as in Example 1.
~2~
-- 14 --
o tQ .___ .
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a
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O h r I f Lo Lo Lo a O
r I a ..... I ... O I I ...
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~Q tQ
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O~L`~ OSLO ~L~
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h I f r-l r-!
0,~ 0
tQ f ,,
tH r-l Pi
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r __ O z; X
~45
-- 15 --
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- 17 -
Example 3-
The following base resin formula-tion is used as
the raw material:
Hexamethoxy~e-thylmelamine 17.93 g
(Cymel 301 I, 100%)
Butyl acetate 9.73 g
Cellulose ace-~obutyrate 1.83 g
(CAB 551,001 from Messrs.
Eastman Chem.)
Silicone resin in an organic solvent 2.80 g
(flow control agent, Byketol Spezial
from Messrs. Byk-Mallinckrodt)
F'low contrAl agent based on a polymer 0.29 g
(Modaflow~, 1% solu-tion; Monsanto)
Acrylic resin having functional
hydroxyl groups 57.30 g
(Paraloid AT 410 , 73%; Rohm Haas)
n-Butanol 10.12 g
100.00 g
The compounds listed in Table 4 are incorporated
in a concentration of 1% by weigh-t into this base resin.
Testing is carried out as described in Example 1. The
results are shown in Table 4. The viscosity change
is given here as %, relative to the initial value of
-the complete resin formulation.
3~
T l A ;;~
it f O f r-l
h O 'ED f (I I l
0~ . __
N I> f N 1
~1 f _ . f _
r Us \I il- O f N 1--
_ .. _. .
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h V - -1' - _ ._ . . _ .. _ . ____
o o~o o cry o
us m o . o
a - .. _ _
f G) I L1 f l if 00 l r I ED O`\ r I O O 1
C\i C\i Oi \i O O O O f O it U \ f
__ . .. _
Us O
f a) V
Lo Lr~ f
Us C\l ~\~ f it 1~i~U~ f COO
h f f f f f f
1 _ ____
_ ---- 'I
ol I f D f 0 r 1 01 to
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X f X X
f f l ~-H
.~ En
f f 0
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En
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19
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Example_4
In -the following experimen-t, -the whi-te finish
formula below ls used as -the raw material.
formula for a white-pi~mented "acrylic/melami e high-
solid finish"
Acryloid AT 400 (acrylic resin having
(75% in MAK) functional hydroxyl
groups; Rohm + Haas) 39.0 % by weight
Cymel 301 ~9.75% by weight
Kronos RN 57 (TiO2 from MessrsO Kronos) 26.0 % by weight
n-Butanol 5.25% by weight
Methyl amyl ketone (MAK) 20.0 /0 by weight
lO0.0 % by weight
Various blocked acid catalysts as well as co-
catalysts are incorpora-ted into -this base resin.
Subsequently, -the white finishes are spread by means of
a doctor blade on aluminium sheets coated with a coil-
coat, in such a way tha-t (af-ter baking) a dry~film
thickness of about 30 results. After a brief air-
drying -time the samples are irradiated for lO minutes
under Phillips TLK 40W/09 fluorescent tubes and -then
baked for 30' at 120C. Af-ter s-toring for 30' 9 the
pendulum hardness according to Koenig is measured.
The test results are compiled in Table 5.
3L2~4~gr7
- 24 -
liable 5
-
Acid catalys-t Co-catalyst Pendulum
hardness
~r:LO mi~u~s
rradia-tion,
nd baking
. .. . ,,_ .,, _
Compound of -the formula
._~ o
none 27
.~ '~S2(cn2~,c~l3
. _ . _ I_
Ditto 1% of hydro- >100
quinone
. . .
Ditto 0.5% of phen- ~100
anthrenequinone
__~ ..... --
Ditto 1% of 2,6-di- 85
-tert.-bu-tyl-4-
m(BthY)lphenol
. _ __ .
Ditto 1% of pentaeryth- 70
rityl tetrakis-
L3-(3,5-di-tert.-
butyl-4-hydroxy-
phenyl)-propionate
... __ .... __ _
Ditto 1.0% of hydro- >100
quinone
0.5% of phen-
an-threnequinone
_ .... __ _ . , _~, --
The amounts of added catalysts rela-te to solid
binder.
