Note: Descriptions are shown in the official language in which they were submitted.
~L45898
The present invention relates to polyfunctional iso-
cyanates free of alkali and urea groups.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is the IR spectrum of a polyisocyanate prepared
by Example 20 of U. S. Patent 3,929,744.
Figure 2 is the IR spectrum of a polyisocyanate prepared
from the same amide polymer as employed above by the process
of the invention.
BACKGROUND OF THE INVENTION
U.S. Patent 3,929,74~, and Wright et al, Journal of
Applied Polymer Science, _ :3305-331 (1976), teach that
polymers containing amide groups can be reacted with excess
aqueous alkali hypochlorite, in the presence of an inert
solvent, at temperatures in the range of 0 to 15C, to
form isocyanates. ~he amide group containing polymers
used in this reaction are sterically hindered polyamides,
namely secondary ~-carbon or tertiary ~-carbon amide
polymers, such as interpolymers of acrylamide or methacryl-
amide with vinyl monomers free of hydroxyl or carboxyl
groups, or the amide homopolymers.
In the prior art processes, a portion of the amide
groups in the starting polymer is converted to isocyanates
;~r ~ 1 ~
898
by the Hofmann degradation reaction, which results in
amide groups and isocyanate groups apparently statistically
distributed along the polymer chain.
The resultant isocyanate group containing polymers
can be used to prepare coating compostions curable at
low temperatures. However, this use requires polymers
of high purity, i.e. polymers which except for unchanged
amide groups and the isocyanate groups, contain, if
possible, no additional functional groups. In addition,
the polyfunctional isocyanates should have an isocyanate
content as high as possible. The prior art polyfunctional
isocyanates do not meet these demands. Because they
are prepared by a Hofmann degradation reaction, i.e. in
an aqueous alkali medium, it is unavoidable that a
portion of the isocyanate groups formed are hydrolytically
decomposed during processing of the reaction mixture. Amino
groups, formed from the unstable carbamic acid, react
with isocyanate groups to form ureas. Consequently, in
addition to unchanged amide groups and the desired
isocyanate groups, the prior art prodllcts also contain
undesirable urea groups. In this connection, reference
,. .-.
is made to the IR spectrum shown on Page 3307 of the
publication of Wright et al supra, which shows a strong
urea band at about 1550 cm 1. In addition, the prior art
polymers also contain free alkali, in quantities found to
be harmful in the further processing of the products. An
additional, important disadvantage of the known products
is their comparatively low isocyanate group content, which
is a result of the above-described side reactions. Thus, e.g.
according to Example 15 of U. S. Patent 3,929,744, there is at
~L145~398
iiLSt 5.2% by weight of isocyanate groups presen~ :~en a
polymer containing amide groups is reacted with sodium
hypochlorite, but only 3.25% by weight of isocyanate
groups can be detected after the lsocyanate has been
isolated by the removal of water. Not only the prior art
products, but the prior art process has disadvantages: In
the prior art process, the reaction takes place in a
mixture of an organic solvent and water. An emulsion
results, which cannot be completely separated into the
aqueous and the isocyanate-containing organic phase,
even with the addition of deemulsifiers. Thus, part of
the desired reaction product is lost in the aqueous phase.
Another disadvantage of this process is the long separation
times, i.e. at least several hours, or sometimes several
days.
DESCRIPTION OF THE INVENTION
An object of this invention is to provide polyfunctional
derivatives of homopolymers or interpolymers of acrylamide
or methacrylamide, that are free of alkali and urea groups.
The interpolymers are interpolymers of acrylamide or
methacrylamide with each other and/o~with vinyl monomers
free of hydroxyl or carboxyl groups, preferably styrene,
methylstyrene, dimethylstyrene, chlorostyrene, and/or an
alkyl acrylate, preferably having 1-15 carbon atoms, such
as methyl acrylate, methyl methacrylamide, butyl acrylate,
butyl methacrylate, decyl acrylate, decyl methacrylate,
dodecyl methacrylate, or dodecyl methacrylate. The invention
-- 3 --
1~5898
also encompasses crosslinked polyfunctional isocyanates
; wherein the acrylamide or methacrylamide polymers are
crosslinked with polyvinyl monomers such as divinyl benzene
or divinyl ethers.
The polyfunctional isocyanates of the invention are
formed from N-chloramide derivatives of the acrylamide or
methacrylamide homopolymers or interpolymers. The N-
chloramides are prepared by chlorination of the appropriate
amide group containing polymer with chlorine.
While N-chloramides are mentioned in U. S. Patent
3,929,744 as intermediate compounds, and it is even con-
jectured there that the N-chloramides could be separated
from the intermediary sodium salt by acidification of the
reaction mixture with a mineral acid, actually the
isocyanate is formed. Because of the difference between
the prior art synthesis and the synthesis of the invention,
the polyfunctional isocyanates of the invention have a
chemical structure fundamentally different from the
prior art products. The products of the invention have
no urea groups, are free of alkalis and have an isocyanate
group content significally higher than that of the prior
art products. In the products of the invention, about
20~ to 100~ of the amide groups in the starting polymer
have been converted to isocyanate groups. The different
chemica~ nature of the polyfunctional isocyanates pursuant
to the invention becomes apparent from a comparison of
the IR spectra shown in Figures 1 and 2.
Figure 1 shows the IR spectrum of a polyisocyanate
synethesized pursuant to Example 20 of U. S. Patent 3,929,744,
~1458913
prepared by Hof~ann degradiation of a copolymer of 15%
methacrylamide and 85% butyl methacrylate with an isocyanate
content of 2.6%. Figure 2 shows the IR spectrum of
a product pursuant to the invention obtained from the
same polymer containing amide groups, but via the
N-chloramide stage, with an isocyanate content of 3.5~.
In contrast to the IR spectrum of the product pursuant
to the invention, the IR spectrum of the product pursuant
to U. S. Patent 3,929,744 has a strong urea band at about
1550 cm 1, the intensity of which can be compared with
that of the isocyanate band. In the IR spectrum of a
polyisocyanate derived from a copolymer of 30% methacrylamide
and 70~ butyl acrylate, which is shown on Page 3307
of the Journal of Applied Polymer Science, 70, one can
also recognize an intensive urea band at about 1550 cm 1.
In the process of the invention, polyfunctional
isocyanate derivatives of the homo- or interpolymers
of acrylamide or methacrylamide are prepared by reacting
an appropriate N-chloramide derivative of the homo- or
inter- polymer with a tertiary amine having a PKa value
of more than 7, in the presence of -an inert solvent,
at temperatures from about 20 to 180C. Preferably, the
N-chloramide derivative is the N-chloramide of an inter-
polymer of methacrylamide and acrylamide or of methacrylamide
or acrylamide with vinyl monomers free of hydroxyl or
carboxyl groups, preferably styrene, methylstyrene,
dimethylstyrene, chlorostyrene, and/or an alkyl acrylate,
preferably having 1-15 carbon atoms, such as methyl
acrylate, methyl methacrylate, ethyl acrylate, ethyl
~i4S898
methacrylate, butyl acrylate, butyl methacrylate, hexyl
acrylate, hexyl methacrylate, decyl acrylate, decyl
methacrylate, dodecyl methacrylate, or dodecylmethacrylate.
Where crosslinked polyisocyanates are prepared using a
polyvinyl crosslinking monomer, the preferred N-chloramide
is a N-chloramide polymer crosslinked with divinyl benzene
or divinyl ether.
The appropriate polymers containing amide groups, which
are required for the preparation of the N-chloramide
derivatives, have in part already been described in U.S.
Patent 3,929,744, and include polyacrylamide, polymeth-
acrylamide, interpolymers of methacrylamide or acrylamide
and styrene, methylstyrene, dimethylstyrene, chlorostyrene
and alkyl acrylates, such as methyl acrylate, methyl
methacrylate, ethyl acrylate, ethyl methacrylate, butyl
acrylate, hexyl acrylate, decyl acrylate and dodecyl acrylate,
as well as the products of the mentioned polymers and co-
polymers, crosslinked by means of customary crosslinking
agents, such as divinyl benzene and divinyl ether. me
homo- and interpolymers useful herein contain 5 to 100 mol %
acrylamide or methacrylamide.
The molecular weight distribution of the homo- and
interpolymers covers a wide range. Typically, the average
molecular weight may vary from 1000 to 10,000 but, prefer-
ably, use is made of polymers with an average molecular
wei~ht from 5000 to 10,000. The crosslinked initial polymers,
for example, can be crosslinked with 1 to 10 mol % of a
divinyl compound
- 6 -
~S8~38
Chlorination of the amide group containing homo- and
interpolymers is preferably carried out with chlorine in
an aqueous-mineral acid suspension at temperatures from
about 0 to 40C. Suitable aqueous mineral acids are
e.g. dilute, aqueous hydrochloric acid, sulfuric acid
and phosphoric acid. Preferably, a start is made with
dilute hydrochloric acid or dilute sulfuric acid aqueous
suspensions of the amide group containing polymers. Chlorina-
tion proceeds exothermally and is preferably carried out
at temperatures from about 0 to about 30~C. The use of
temperatures higher than about 40C. is disadvantageous,
because noticeable quantities of carboxyl groups are
formed by hydrolysis. Chlorination can be carried out at
ambient or at elevated pressures. The required reaction
time decreases with increasing pressure, but, for reasons
of ecomony, the preferred pressure range is between
about 1 and about 6 atmospheres gage pressure. Since
chlorination is taking place in a heterogeneous phase,
care must be taken, that the suspension is properly mixed.
The reaction mixture should be diluted, at least to such
an extent, so that it can be stirred, or mixed in some
other way, without any difficulties. The preferred dilution
of the reaction batch is about 100 to 200 grams of amide
group containing polymer per liter of water, or aqueous
mineral acid. When the above processing conditions are
maintained, chlorination is completed in about 1/4 to 2
hours. Depending upon the composition of the amide group
ll~S898
c~nlaining polymers, about 20 to 100~ of the amide groups
are transformed into N-chloramide groups under these condi-
tions. The only solid substance present in the suspension,
after chlorination is completed, is the modified polymer,
which can be separated from suspension by conventional
means, for example, by filtering or centrifuging.
The selection of a suitable base is of a decisive
factor for the success of the process step pursuant to
the invention wherein the N-chloramide is converted to the
isocyanate. Tertiary amines of a certain basicity are
used. The basicity constant PKa is employed as a measure
of the basicity. Tertiary amines suitable for the process
pursuant to the invention should have a minimum basicity
corresponding to a PKa value of more than 7. Suitable
tertiary amines are aliphatic, cycloaliphatic and aromatic
amines such as (the pertinent PXa values, in each case at
20C, are given in parentheses) trimethylamine (9.90),
triethylamine (10.74), tri-n-butylamine (9.89), 2.4.6-
trimethylpyridine (7.45-7.63), tri-n-propylamine (10.74),
ethyldimethylamine (10.06), propyldimethylamine (10.16),
isopropyldimethylamine (10.38), methyldimethylamine (10.43),
butyldimethylamine (10.31), 2.3.4.5-tetramethylpyridine (7.78)
and 2.3..4.5.6-pentamethylpyridine (8.75). Preferred tertiaxy
amines are trimethylamine, triethylamine, tri-n-propylamine
and tri^-n-butylamine. The PKa values can be found in
customary handbooks. In the case of aliphatic, tertiary
amines, special reference is made to L. Spialter et al.-j
The Acyclic, Aliphatic Tertiary Amines, The McMillan Co.,
~l~S898
New York (1965~ and, in the case of substituted pyridin~,
to Xlingsberg, Heterocyclic Compounds Pyridine and Derivatives
part 2, Interscience Publishers, Inc., New York (1961).
The basicity of the tertiary amine employed is
significant for the progress of the reaction, i.e. when
polymers with the same N-chloramide content are used,
the isocyanate yield is lower, the lower the PKa value of
the tertiary amine.
The tertiary amine is employed in quantities of at
least about one molar equivalent per mol of N-chloramide
constituent in the polymer. The preferred equivalence
ratio of N-chloramide to tertiary amine is about 1:1 to
about 1:4. Larger quantities of tertiary amine can be
used without being harmful, but should be avoided for
reasons of economy.
The N-chloramide conversion step is conducted in the
presence of an organic solvent. In the selection of the
organic solvent, care must be taken that, under the
conditions of the reaction, the solvent is inert, i.e.
that it will react neither with the N-chloramide group,
nor with the isocyanate group, nor wi~h the tertiary amine
being used. Suitable solvents include, for example,
methylene chloride, l,l-dichloroethylene, chloroform,
carbon tetrachloride, trichloroethylene, tetrachloroethylene,
pentane, hexane, cyclohexane, heptane, octane, benzene,
toluene, ethyl benzene, chlorobenzene, xylene, dichloro-
benzene, diethyl ether, tetrahydrofuran, dioxane, methyl
acetate, butyl acetate, and methyl propionate. The
g _
~1~589~
preferred solven~s are toluene, xylene, chlorobenzene,
tetrachloroethylene, carbon tetrachloride, cyclohexane,
dioxane, chloroform and butyl acetate.
The preferred dilution of the reaction batches is
about 100 to 200 grams of N-chloramide-containing polymer
per liter of solvent, but lower, or higher concentrations
can also be used.
In the process of the invention, the reaction
temperatures for the N-chloramide conversion step are
in the range from about 20 to about 180C. Essentially,
the optimum temperature depends upon the specific
polymer used, its N-chloramide content, and the basicity
of the tertiary amine. In the case of some starting
materials, the reaction will start at room temperature
and at least in part even very vigorously. As a rule,
the reaction is carried out at the boiling temperature
of the solvent used. The preferred reaction temperatures
are in the range from about 65 to aboubt 135C.
In the N-chloramide conversion process of the
invention, the required reaction times are brief, as a
rule only a few minutes. However, long reaction times,
e.g. a reaction time of one hour, can be used without
being harmful.
In conducting the N-chloramide conversion of the
invention it is expedient to disperse the N-chloramide-
containing polymer in the solvent and then to add the required
minimum quantity of tertiary amine. In some cases, the
-- 10 --
ll~S898
reaction starts immediately, in other cases, the temperature
is quickly raised to the desired reaction temperature. As
a rule, the boiling temperature of the solvent is used.
If required, heating is continued for a longer period
of time with reflux and, after the reaction has taken
place and the reaction mixture has cooled, the resultant
tertiary amine hydrochloride is separated, for example
by filtration and the product isolated, e.gO by concentration,
the filtrate in a vacuum.
The resultant polyfunctional isocyanate derivatives
of the acrylamide or methacrylamide homo- or interpolymers,
free of alkali and urea groups can be used to form film
forming compositions such as films and coatings, in parti-
cular, lacquers. Film forming compositions and the resultant
lS films can be obtained by admixing and reacting the
polyisocyanate with conventional isocyanate group reactive
active hydrogen containing reactants such as, for example,
amines, acids, and alcohols.
U. S. Patent 3,929,744 and Wright et al, supra describe
coating composition that can be baked, or cured, at low
temperatures. However, these prior art compositions
are inferior in quality as compared to the comparable
polymer composition derived employing the polyisocyanates
of the invention. For example, when the prior art polymeric
isocyanates are reacted, i.e. crosslinked with polyols,
one generally obtains turbid, to slightly turbid products
of comparatively low hardness. The turbidity is probably
due to the urea groups of the polyisocyanate. In contrast,
--11--
114~8~8
th~ polyisocyanates of the invention are clear and~ when
crosslinked with polyols, also ~esult in clear products
of high hardness. Consequently, the polyisocyanates of
the invention are excellently suited for the preparation
of coating compositions, particularly those formed by
admixing polyols.
There follows a number of Examples which are to be
considered illustrative rather than limitin~. All parts
and percentages are by weight unless otherwise specified.
All temperatures are degrees Centigrade unless otherw;~se
$peci'fied.
A Pre~aration of the Polymeric N-Chloramide
_____________________________________________
Procedure A
lO g of an interpolymer of io parts methacrylamide, 50
parts methyl methacrylate and 40 parts butyl acrylate were
dispersed in lO0 g of 5~ hydrochloric acid. After that,
chlorine was passed through for 4 hours at 15 to 20C.
After stripping of the excess chlorine with nitrogen, the
polymeric N-chloramide was filtered off with suction,,
washed until neutral with distilled w~ter and dried at
35C in a vacuum (30 Mbar).
Procedure B
lO g of an interpolymer of 20 parts methacrylamide, 40
parts methacrylate and 40 parts butyl acrylate were chlorinated
for 30 minutes at 20C with a chlorine pressure of 4 bar
in lO0 g of 5~ hydrochloric acid. The N-chloramide was isolated
as indicated under Procedure A. 10.35 g of polymeric
-12-
~1~5898
N-chloramide with an active chlorine content of 6.4% were
obtained, i.e. 83% of the amide groups were chlorinated.
B Pre~aration_of the Polymeric Isocyanate
____________________ _________________~____
Example 1
10 g of polymeric N-halogen amide, prepared by chlorinating
an interpolymer of 10 parts methacrylamide, 50 parts methyl
methacrylate and 40 parts butyl acrylate, with an active
chlorine content of 3.1~, were suspended in 100 ml of
toluene. After the addition of 3 g of triethylamine,
the mixture was quickly heated to 100C and left at this
temperature for 30 minutes. After that, excess triethyl
amine and 20 ml of toluene were distilled off. After
cooling, the precipitated triethylamine hydrochloride
and other undissolved constituents were separated and
the filtrate concentrated in a vacuum. 9.5 g of resin free
from alkali and urea groups, with an isocyanate content
of 3.4~ remained.
Example 2
The reaction was carried out analogous to Example 1, except
that, instead of the toluene, the same quantities of chloro-
benzene, dioxane and acetic butyl ester were used in each
case. Table 1 shows the quantities of polymeric isocyanate
free from alkali and urea groups that were isolated, together
with their ~CO contents.
114589~3
Table 1
Quantity by weight of polymeric
Reaction Medium iso~yanate NOO content (%)
chlorokenzene 9.3 g 3.35
dioxane 9.5 g 3.2
acetic butyl ester 9.25 g 3.5
Example 3
10 g polymeric N-halogen amide, prepared by chlorinatir,g an
interpolymer of 20 parts methacrylamide, 40 parts methylmeth-
acrylate and 40 parts butyl acrylate, with an active chlorine
content of 6.4%, were, as in Example 1, suspended in toluene
and converted to the polymeric isocyanate with an addition
of 5 g of triethylamine. 9:25 g of a resin free from alkali
and urea groups, with an NCO content of 4.7%, were obtained.
lS Example 4
Additional polymeric N-chloramides were, as described in
the above examples, suspended in toluene and converted to
the polymeric isocyanates with triethyl amine.
Table 2 shows the composition of the ~polymers, the chlorine
content of the polymeric N-halogen amides, as well as the
NCO co~tent of the polymeric isocyanates free from alkali
and urea groups, that resulted therefrom.
- 14 -
~1~5898
Table 2
Converted Weighed
Chlorine quantity of Triethyl- quan- NCO
Pcl~ composition content N-chlorarnide amine tity collcent
~ g g % %
10 ~ methacrylamide 3 10 2 9.6 3.2
90% decyl acrylate
30% methacrylamide
30% methylmethacrylate 10.1 10 10 8.8 5.5
40% butyl acrylate
30~ methacrylamide
70% butyl acrylate 11.2 10 10 8.6 5.6
Example 5
As in Example 1, 10 g of polymeric N-halogen amide, prepared
by chlorinating an interpolymer of 20 parts acrylamide and 80
parts methylmethacrylate, with an active chlorine content of
7.7%, were converted to the polymeric isocyanate in toluene,
with an addition of 5 g of triethylamine.
4.8 g polyisocyanate free from alkali and urea groups, with an
NCO content of 4.7~ were isolated.
Example 6
10 g of polymeric N-halogen amide of the composition as given
in Example 3 were suspended in 50 ml of toluene and a
solution of 3 g of trimethyl amine in 50 ml toluene added
thereto. The mixture was quickly heated to reflux temperature
(110C). During heating, excess trimethyl amine escaped
in gaseous form. Boiling was maintained for 1 hour, followed
by cooling, removal of trimethylamine hydrochloride by suc-
tion filtration and concentration of the filtrate in a vacuum.
The resulting residue was 9.3 g of resin free from alkali and
urea groups, with an NCO content of 4.5~.
11451398
Example 7
10 g of polymeric, crosslinked N-halogen amide, prepared by
chlorinating a polymethacrylamide crosslinked with 5% divinyl
benzene and with an active chlorine content of 17~, were
suspended in 100 ml of toluene and, after addition of 20 g
of triethyl amine, treated for 30 minutes at 110C. Cooling
was followed by suction filtration and washing of the residue
with chloroform to remove the triethylamine hydrochloride.
7.5 g of a white powder free from alkali and urea groups,
and with an NCO content of 9.8% remained.
Example 8
A mixture of 10 g of polymeric, crosslinked N-halogen
amide of the composition as given in Example 7, 26 g of
tripropyl amine and 100 ml of chlorobenzene was heated to
130C for 10 minutes. This was followed by suction
filtering, washing with chlorobenzene and drying of the
residue. 7.7 g of polymeric, crosslinked isocyanate free
from alkali and urea groups, with an NCO content of 9.6%,
were obtained.
Examples 9-15
Following the process described in Example 1, polyfunctional
isocyanates free from alkali and urea groups, with an iso-
cyanate content in a range from 2.8 to 4.8% by weight were
prepared from methacrylamide, methylmethacrylate and, as
the case may be, butyl acrylate, butylmethacrylate, methyl
acrylate, or 2-ethylhexyl acrylate. The resulting products
were processed into lacquers by reacting them with a polyol.
- 16 -
~l~S898
The polyol used was the commercial product "Setalux 115~'TM of
the firm Synthese, Bergen, OP 200 M, Holland. It involves a
polyester grafted with hydroxyl acrylates, with a molecular
weight of 2150 - 220, an OH number of 65-71, and an acid
number of 3-4.
A 50% by weight solution of the polyfunctional isocyanate
was dissolved in toluene and mixed with an equivalent quantity
of a 50% by weight solution of the polyol in xylene/butyl-
glycol acetate. If necessary, the mixture was brought to
processing viscosity by the addition of more toluene. 0.5%
dibutylin dilaurate was used as catalyst. This lacquer prep-
aration was applied to sheets of glass with a lacquer tool or
a film pulling spiral. After a 10-minute airing period, the
films were baked for 30 minutes. Clear, bright films were
obtained in all cases.
The resulting films are characterized by their hardness and
the so-called rub test. ~The pendulum hardness according to
Koenig was measured pursuant to DIN 53 157. With the rub
test one determines the solubility, or swelling of the film
in a solvent, e.g. methylisobutyl ketone. In the test a finger
is wetted with the solvent and moved back and forth over the
film under pressure. A determination is made of the number of
back-and-forth movements of the finger wet with solvent,
which are required to bring about signs of film dissolution.
Films showing no dissolution after 100 back-and-forth movements
are well crosslinked and are considered good. Table 3 lists
the polyfunctional isocyanates used, their isocyanate contents,
the crosslinking temperature, the pendulum hardness, and
the data obtained in the rub test.
- 17 -
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U~~ ~ ~ ~ ~ ~ ~~ ~ ~
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Q. o~1 1 o co o ~1
U E~ . 11 11 11
.~ I
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F~ o 3 d~P o~o o~p ~p o~O o~O o~o
0~ CO U~GD ~ In~
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U~ o o O O O
3 ~ ~ r ~ ~ O ~
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. 18
. 1~l45898
Examples 16 and 17 (ComParative Examples)
A polyfunctional isocyanate pursuant to the invention, free
from alkali and urea groups, and the product obtained according
to Example 20 of U. S. patent 3,929,744 ("Batch C"), each
made from 15% by weight of methylacrylamide and 85% by
weight butyl methacrylate, were, after four weeks, cross-
linked with the polyol "Setalux 1151" at different baking
temperatures, in the manner described for Examples 9-15.
The polyisocyanate pursuant to the invention was a brownish,
clear, viscous resin with an isocyanate content of 2.1%
by weight, that was unchanged after the four weeks. The
product obtained according to the process of the U. S.
patent was a brownish, turbid, viscous mass with an original
isocyanate content of 2.6% by weight. After the four ~
weeks, the isocyanate content had declined to 2.0% by weight.
The results obtained are compiled in Table 4, which clearly
shows the superiority of the products pursuant to the
invention and of the coating composition obtainable
therefrom.
Table 4 .~
Baking Example 16 Example 17
tem~eratures Rub Hard- R~b Hard-
C Test ness Re~ark Test ness Remark
<20 16 film turbid
100 ~25 25 turbid
120 ~25 62 clear25-30 36 turbid
130 50 120 clear
140 25-30 48 slightly turbid
150 90 135 clear~30 57 slightly turbid
--19--
S8~
Example _
A 50% by weight solution of a polymeric isocyanate prepared
from methyl methacrylate, butyl acrylate and methacrylamide
(50:40:10), with an isocyanate content of 3.1% by weight,
was mixed with equivalent quantities of hexamethylene
diamine. Crosslinking started immediately.
Example 19
, =
A polyisocyanate with an isocyanate content of 3.1% by
weight, obtained pursuant to Example 1, was corsslinked
with a blocked amine. Schiff's base (M,N'-dicyclohexylidene-
1,6-hexamethylene diamine) obtained from hexamethylene
diamine and cyclohexanone with the exclusion of atmospheric
moisture was used as the blocked amine. 50% by weight
solutions of the polyisocyanate and of the blocked amine
in toluene were mixed with one another. The resulting
stable solution was spread on a sheet of glass. The Schiff's
base was hydrolized by atmospheric moisture, the amine
reacted with the polyisocyanate, and a clear film was
obtained.
.
-20-
_ . ... . _ _ .. .. . ..
