Note: Descriptions are shown in the official language in which they were submitted.
~037639
The invention relates to a process for the preparation of hard
cured resins by copolymerization of polyisocyanates with ethylenically
unsaturated compounds, which process can be used for the manufacture of
articles such as castings, pottings and laminates.
It is known that isocyanurates can be prepared by polymerization
of isocyanates. Further it has been suggested that copolymers could be
prepared by copolymerization of polyisocyanates with vinyl compounds having
an electron-attracting substituent, such as vinyl acetate, in the presence
; of an anionic catalyst such as a tertiary amine or an alkyl metal compound.
However, when this reaction was repeated, it was found that the vinyl acetate
did not contribute to the polymerization reaction, so that the product had
no technical utility.
The invention provides a process for the copolymerization of a
polyisocyanate and an anionically polymerizable ethylenically unsaturated
compound, with the use of a novel catalyst for this type of copolymerization.
The invention is defined as a process for the preparation of hard cured resins
by copolymerization of a mixture of a polyisocyanate and an anionically
polymerizable ethylenically unsaturated compound in the presence of a cata-
lyst, wherein a mi~ture comprising the polyisocyana~e and the ethylenically
unsaturated compound, or a liquid prepolymer of such a mixture, is poly-
merized in the presence of a catalyst composition comprising as catalyst a
Mannich base which is a phenolic compound having in the molecule at least
one tertiary aminomethylene group in which the methylene group is directly
attached to a carbon atom of the phenolic nucleus.
The invention further envisages the incorporation of additional
ionic copolymerization catalysts (cocatalysts) such as epoxides.
The phenolic compound as defined above is a Mannich base which
can be prepared from a phenol, preferably a monohydric mononuclear phenol
such as hydroxybenzene, formaldehyde, and a secondary amine, for example
'
?~Q37~
dimethyl amine, dietha amine, methyl ethanol amine, or mixtures of
secondary amines. ~xamples of preferred catalysts are dimethylaminomethyl
phenol (ortho-, para- and mixtures thereof) and 2,4,6-tris~dimethylamino-
methyl)phenol, such as the commercial products DMP-10 and DMP-30, respectively.
A polyisocyanate as used in the present irlvention is defined as
an organic isocyanate having on average more than one isocyanate group per
molecule. Both aliphatic and aromatic polyisocyanates may be used. Ali-
phatic and aromatic polyisocyanates are defined as compounds in which each
isocyanate group is directly attached to an aliphatic or aromatic group,
respectively.
Suitable aromatic polyisocyanates are, for example, meta- and
para-phenylene diisocyanate, toluene-2,4- or 2,6-diisocyanate and mixtures
of these isomers, r,aphthalene-1,5-diisocyanate, diphenylmethane 4,4'-
diisocyanate, triphenylmethane-4,4',4"triisocyanate, triphenyl dimethyl
triisocyanate, diphenyl 4,4'-diisocyanate, 3,3'-dichloro diphenyl 4,4'-
diisocyanate, 3,3'-dimethoxy diphenyl 4,4'-diisocyanate, 3,3'-dimethyl di-
phenyl 4,4'diisocyanate,i3,3'-bisphe~yl diphenyl 4,4'-diisocyanate, 3,3'-
dimethyl diphenylmethane 4,~-diisocyanate, diphenyl ether 4,4'-diisocyanate,
N,N'-bis(4-methyl phenyl) uretidindion 3,31-diisocyanate, and mixtures of
these isocyanates. Examples of aliphatic polyisocyanates are butane 1~4-
diisocyanate, hexane l,6-diisocyanate, 2,2,4-trimethylhexane diisocyanate,
dodecane 1,12-diisocyanate, m-xylene diisocyanate, cyclohexane diisocyan~te,
dicyclohexylmethane-4,4'diisocyanate, 2-butene-1,4-diisocyanate and diethyl
sulphide-2,2'-diisocyanate. Mixtures of aliphatic polyisocyanates, or mix-
tures of aliphatic and aromatic polyisocyanates may also be used. The
polyisocyanate may be a crude product, or may have been purified, for example
by distillation or crystallization. Preference is given to aromatic poly-
isocyanates, in particular those having an alkylidene group, preferably a
methylene group, between two isocyanate-substituted aromatic nuclei,
-- 2 --
~03~ 9
preferably isocyanate-sub~tituted phenyl nuclei.
Very good results can be obtained with polyisocyanates containing
as the major component diphenylmethane 4,4'-diisocyanate, such as pure
diphenylmethane 4,4t-diisocyanate, liquefied diphenylmethane 4,4'-diiso-
cyanate, or a mixed polyisocyanate containing 40-60 ~w diphenylmethane 4,4~-
diisocyanate, 15-30 ~w triphenyl dimethylene triisocyanate, and 10-20 ~w
tetraphenyl polymethylene polyisocyanates.
The anionically polymerizable ethylenically unsaturated compound
has preferably no active hydrogen atoms, and may be a compound of the
formula
H >c=6 R~ wherein R is a radical of the group consisting o~ an
aromatic hydrocarbon radical having 6-7 carbon atoms, such as phenyl or
tolyl; a -O-C-R' radical wherein R' is a saturated alkyl radical having 4 to
14, preferably 8 to 10, more preferably 9 carbon atoms; a -C - N radical;
a - ~OR" radical wherein R" is an alkyl radical having 1-4 carbon atoms;
a -C=CH2 radical; or a -C~ =CM2 radical; and in which formula Y is hydrogen
oCH3
if R is an aromatic, -O-~-RI, cyanide~ or vinyl radical, and is methyl or
hydrogen if R is a -ICI-OR'' radical.
The preferred ethylenically unsaturated compounds having no active
hydrogen atoms are vinyl aromatic hydrocarbons such as styrene and vinyl
toluene; styrene is preferred, in particular in view of the superior heat
resistance of the polymerized products.
Other examples of ethylenically unsaturated compounds having no
active hydrogen atoms as defined above are: vinyl esters of saturated ali-
phatic monocarboxylic acids in which acids the carboxyl group is attached
to a tertiary or quaternary carbon atom, and which acids have 9 to-:11,
preferably 10 carbon atoms per molecule; acrylonitrile; methyl, ethyl,
-- 3 --
1~37~39
propyl and but~l esters of acrylic acid or methacrylic acid; butadiene
and isoprene. Such other ethylenically unsaturated compounds can be used
either as the only unsaturated compounds, or in admix~ure with the preferred
unsaturated compounds, for example as additives to styrene or vinyl toluene,
preferably in minor amounts, for example to modify mechanical properties
of the polymerized products.
In a modification of the process according to the invention an
ethylenically unsaturated compound containing one or more hydroxy groups
may additionally be incorporated into the monomer mixture; preferred are
hydroxy-containing esters of acrylic acid or methacrylic acid such as
hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,
or an 1:1 molar adduct of acrylic acid and glycidyl esters of alpha-branc~ed
saturated aliphatic monocarboxylic acids having 9-11 carbon atoms per mole-
cule. Such hydroxy-containing unsaturated compounds may be used to modify
handling characteristics of the mixture during the polymerization or to
modify properties of the polymerized product.
Epoxides, preferably those which are liquid at ambient temperature,
can be used in the process of the invention as co-catalysts for the poly-
merization. Preferred are epoxides which are soluble in the polyisocyanate.
The epoxide may be a monoepoxide or a polyepoxide, i.e. a compound having
more than one epoxy group per molecule; mixtures of monoepoxides and poly-
epoxides may also be used. Suitable monoepoxidesare epichlorohydrin, ~ut~l
glycidyl ether, and phenyl glycidyl ether. Suitable polyepoxides are poly-
glycidyl ethers of 2,2-bis~ hydroxyphenyl)propane, in particular those
having an epoxy equivalent weight of between 170 and 250. The use of epoxides
as co-catalysts improves the heat distortion properties of the polymerized
product. Other co-catalysts which may be used are lactones~ such as pivalo-
lactone, which may be used alone or in combination with epoxides.
The amount of ethylenically unsaturated compound is in general from
-- 4 --
~0376;~
10 to 70, preferably from 15 to 65 per cent by weight of the polyisocyanate.
In particular, the use of styrene in amounts of from 40 to 60, especially
50 per cent by weight of polyisocyanate can be recommended, as those weight
ratios combine good overall performance of the copolymer with acceptable
potlife of the monomer mixture.
The Mar~ich base catalyst as defined above is preferably used
in an amount of from 0.01 to 10, more preferably in an amount of from 0.1
to 7, in particular 1 to 4 per cent by weight on combined weight of poly-
isocyanate and ethylenically unsaturated compound, or liquid prepolymer
thereof. The potlife at ambient temperature can be varied to some extent
by variation of the amount of catalyst; in general it can be stated that at
low amounts of catalyst the potlife is reasonable, but the polymerized
product might be somewhat hazy, whereas at high amounts of catalyst a clear
polymerized product is obtained, but at the cost of a very short potlife.
A convenient method to improve the potlife will be given further below.
The amount of epoxide is preferably below 6 per cent by weight on
combined weight of polyisocyanate and ethylenically unsaturated compo~mds,
or liquid prepolymer thereof, and is more preferably between 3 and 5 per
cent by weight in case that the ethylenically unsaturated compound is styrene.
In the process according to the invention the copolymerization
usually starts at ambient temperature after the catalyst and, optionally,
a co-catalyst have been added to the mixture of monomers, or liquid pre-
polymer thereof. It is preferred that during some hou~s, say 10-20 hours,
the mixture then be kept at ambient temperature or slightly elevated tem-
perature, say 30-60C, until the product is a solid mass which can be handled
easily without using a mould, and the product formed then be heated at
temperatures from 100 to 250C, preferably from 150 to 220C, more preferably
from 180 to 210C during 2 to 10 hours, this post-cure is essential to com-
plete the polymerization and to impart optimal thermal properties to the
-- 5 --
1~37639
polymerized product. Other cure schedules may be envisaged, but the
essential point is that the polymerization reaction is started at relatively
low temperatures, and completed at the elevated temperatures indicated above.
To improve the potlife at ambient temperature, small amounts of
an acyl chloride, preferably benzoyl chloride, may be added. The amount of
acyl chloride is preferably from 0.05 to 1.0, more preferably ~rom Ool to
0.25 per cent by weight of the mixture of polyisocyanate and ethylenically
unsaturated compourd; when benzoyl chloride is used in these amounts the
potlife at ambient temperature (with the use of DMP-30 or DMP-10 as catalyst)
can easily increase from about 3-5 minutes to a level of 30-150 minutes~ -
as demonstrated in examples below.
In the process according to the invention other, non-reactive
components may be incorporated into the monomer composition, such as solvents,
fille~s, pigments, dyes, fibrous materials, such as glass fibres, glass cloth
and glass mats, and extenders such as asphaltic bitumen, coal tar, aromatic
extracts of petroleum distillates, or polymers such as polyvir~l chloride.
The process according to the invention is of particular importance
for the manufacture of articles such as castings, impregnated electrical
equipment, or laminates. In the twolast menti;one~ applications the electrical
equipment or the fibrous mass is potted, dipped, or impregnated with the
mixture of monomers, catalyst, modifiers and optionally, other components,
whereafter the composite is allowed to solidify by copolymerization of the
active ingredients as described hereinbefore.
In particular when styrene is used as the ethylenically unsaturated
compound polymerized products having a very high thermal-stability can be
obtained, for example products having heat distortion temperatures above
200C and having remarkable stability at temperatures above 250C, as indicated
by low weight losses at heating for some days at 280C. Such pol~merized
products also have attractive electrical properties, such as low dielectrical
-- 6 --
~37~3~
constant, low loss factor, and low variation of those properties as functions
of temperature or frequency.
With regard to polymers prepared as described above wherein
styrene is used, it is remarkable that the catalyst as defined will not
polymerize styrene alone. Further, there is no neecl to add a free-radical
polymerization initiator; in an experiment in which the free-radical
initiator azo bis~isobutyronitrile) was added, the cured resin contained gas
bubbles, which is undesirable.
The mixtures o~ polyisocyanate and ethylenically unsaturated
compound have usually a very low viscosity, and it may be desirable to in-
crease the viscosity, for example to improve impregnating characteristics, to
prevent dripping, or to decrease the settling of fillers. The viscosity of
the mixtures may in some instances be increased by a prepolymarization in the
presence of a catalyst, such as an active tertiary amine, for example tri-
ethylene diamine, or a quaternary ammonium hydroxide, whereupon the catalyst
is inactivated by addition of a small excess of an acyl chloride, preferably
benzoyl chloride, or of chloranil. The liquid mixture having increased vis-
cosity can then be kept at ambient temperature during some time, before the
Mannich base catalyst is added and the mixture is used for the manufacture
of the relevant articles. This method to increase the viscosity is parti-
cularly useful when the polyisocyanate is a mixture comprising 40-60 weight
per cent of diphenyl methane 4,4~-diisocyanate, 15-30 weight per cent of
triphenyl dimethylene triisocyanate, and 10-20 weight per cent of tetraphenyl
polymethylene polyisocyanates.
The invention is illustrated by some examplesO
Parts and percentages therein are by weight, unless otherwise
indicated.
Component codes or abbreviations are explained below.
DMP-10: dimethylaminomethyl phenol ~mixture of ortho and para)
DMP-30: 2,~,6-tris(dimethylaminomethyl)phenol
76~
Polyether A: a polyglycidyl ether of 2,2-bis(4-hydroxyphenyl)-
propane, havir,g an epoxy equivalent weight of 190, and being liquid at
ambient temperature.
BS: British Standard.
MDI: diphenylmethane-4,4'-diisocyanate
Polyisocyanate CD: a commercial liquefied MDI.
Polyisocyanate 30: a commercial MDI-based polyisocyanate containirg
about 50 ~w MDI, about 22 ~w triphenyl dimethylene triisocyanate, and about
15~w tetraphenyl polymethylene polyisocyanates, the remainder being composed
of minor amounts of impurities.
~MPLE I
Castings were prepared by mixing 2 parts by weight o~ polyiso-
cyanate CD, 1 part by weight of styrene, and catalysts and co-catalysts as
indicated in Table I below (in ~w on total weight of polyisocyanate and
styrene), and curing durir,g 16 hours at ambient temperature and subsequently
3 hours at 180C. Details regarding product properties are given in Table I.
Table I
Co-catalyst Catalyst Properties of castings
Poly- phenol DMP-30 Appearance Impact Heat weight loss
ether ~w ~w resis- dis- at 280C~ %
A tance tor- after after
~w (notched)tion 1 day 3 days
BS Izod, temp.,
kg.cm/cm2 C
4 2 0.3 slightly 2.3 >250 3.0 4.0
hazy
2 4 0.3 cle~r 1.9214 4.9 7.9
2 2 0.3 hazy 2.9~250 3.0 3.8
4 - 0.5~ hazy 3.1~250 4.0 5.0
4 - 1.0~ clear 2.9~250 2.8 3.6
__ _
~ added in admixture with an equal weight of benzyl alcohol.
~376~9
EI~AMPLE II
Castings were prepared by mixing 2 parts by weight of Polyiso-
cyanate GD, 1 part by weight of styrene, and catalysts, co-catalysts and
i~ibitors (in % w on total weight of polyisocyanate and styrene) as indi-
cated in Table II below, and curing during 16 hours at ambient temperature
and subsequently 3 hours at 180C. Details regarding properties are given
in Table II. This table also demonstrates that the potlife can be increased
considerably by addition of small amounts of benzoyl chloride.
Table II
Catalyst,Co-catalystInhibitor,Potlife Proper ies of castings
%w Polyether A ~w at 20C Appearance ~icat
~w Benzoyl (min.) softening
chloride temp.
(O.t mm), C
3% DMP-30 4 - 5 clear 196
3% DMP-30 4 0.25 150 slightly hazy 202
4% DMP-30 4 0.25 90 " "
6% DMP-30 4 0.25 30 clear 217
1% DMP-10 4 - 10 hazy
2% DMP-10 4 - 4 clear
3% DMP-10 4 - ` 3 clear
3% DMP-10 4 0.25 240 clear 196
4% DMP-10 4 0.25 100 clear
5% DMP-10 4 0.25 45 clear
6% DMP-10 ~ 4 0.25 30 clear 198
* This experiment was repeated with the diference that the Polyisocyanate CD
was replaced by MDI. The potlife at 20C was 30 minutes, the cured casting
was clear and had a Vicat softening temperature (0.1 mm) of 217C.
EXA~LE III
Castings were prepared by mixing 2 parts by weight of Polyisocyanate
CD and 1 part by weight of styrene with 2 7~w DMP-30 as catalyst, ~ 7'w Poly-
ether A as co-catalyst and 0.1 ~w benzoyl chloride as potlife improver (all
per cents by weight are based on total weight of polyisocyanate and styrene)
and curing during 16 hours at ambient temperature and subsequently 3 hours
_ g _
at 2000C. 10376;~
Mechanical, electrical, thermal and chemical properties were as
follows:
Appearance.............................. slightly hazy
Hardness ~Barcol).................................. 48
Heat distortion temperature..................... 238C
Vicat softening temperature: at 0.1 mm.233C
at 0.2 mm.250C
Weight loss after heating at 280C during
1 day ... 2.7 5~w
2 days... 3.3 ~Ow
3 days... ;3~5~w
4 days... 3.9 7tW
6 days... 4.7 ~w
7 days... 5.0 ~w
Appearance after heating at 280C during
6 days... clear
Tensile strength, kg/cm2.......................... 630
elongation, %..................................... 4.5
~modulus, kg/cm2............................... 16,000
~lexural strength, kg/cm2....................... 1,000
~modulus, kg/cm2............................... 36,000
Compressive strength, kg/cm2
at 5% deformation...................... l,100
at 15% ~ ........................... 1,700'`
at 25% ~ ............................. 2,100
at break............................... 3,100
~modulus, kg/cm2............................... 23,400
Deformation at break, %............................ 40
Impact resistance, kg.cmlcm2 BS Izod notched............ 2~.9
unnotched....................... 17
Shrink, % total.......................................... 8.5
before gelation.................................... 4.0
after gelation..................................... 4.5
-- 10 --
~LVolu~e resistivity, Qcm, 500 V,
at 20C 8.5 x 1015
at 127C lol5
at 155C 5 x 1014
at 165C lol4
at 180C 6 x 1013
at 200C 2 x 1013
Dielectrical constant (1000 c/s) and tg ~
20C 2.94 0.1 x 10-2
150C 2.97 0.3 x 10-2
220C 3.02 0.5 x 10-2
Chemical resistance
Weight increase (~Ow) after exposure during 1 2 4 weeks
water 1.4 1.6 1.7
2 ~Ow NaOH 1.4 1.6 1.7
20 ~w NaO~ 0.7 0.8 0.8
S ~w acetic acid 1.4 l.6 1.7
2.5 ~w H2S04 1.4 1.6 1.7
methyl ethyl ketone O O O
EXAMPLE IV
Laminates were prepared by impregnating at ambient temperature,
10 layers of 200 g/m2 plain -weave electrical glass cloth having an epoxy
silane finish with the same monomer/catalyst/potlife improver mixture as in
Example III. The laminates were cured during 16 hours at ambiert temperature
and subsequently 3 hours at 200C. The properties of the cured laminates
were as follows:
Glass content~ ~w.............................. ..~64.5
Flexural strength, kg/cm2
at ambient temperature.......... 5,500
at 150C........................ 4,270
at 200C........................ 3,660
at 250C........................ 3,000
after 2 hours in boiling water.. 5,050
Flexural E-modulus at ambient temperature, kg/cm2...257,000
Tensile strength, kg/cm~....................... 4,270
Burning properties (ASTM D 635)................ self-extinguishing
time to extinguishing, sec............. 15
Solder resistance at 260C..................... good *
~: no blistering or delamination
Adhesion of 70 micro ~cQ ~ , kg/cm
at ambient temperature..................... l.35
at 150C................................... 1.26
after contact with solder at 260C......... 1.35
Dielectrieal eonstant (1000 e/s) and tg ~
20C 4.35 0.1 x 10-2
150C 4.39 0.4 x 10-2
210C 4.44 0.7 x 10-2
E~AMPLE V
:
Castings were prepared from mixtures of 2 parts by weight of
Polyisoeyanate 30 and 1 part by weight of styrene, with 2 ~w DMP-30 as
eatalyst and 4 ~w Polyether A as co-catalyst, and curing during 16 hours
at ambient temperature and subsequently 3 hours at 200C. The performanee -
eompared with the same composition wherein the Polyisoeyanate 30 was replaeed
by Pol~isoeyanate CD - is summarized in Table III.
Table III
Polyisocyanate _
CD
Potlife, minutes 300 50
Heat distortion temperature, C 246 238
Hardness, Barcol 52 48
Impaet resistanee, kg/cm2
BS Izod notched 2.2 2.9
unnotehed 16.7 17.0
Shrink, %
Total 6.8 8.5
in liquid phase 4.5 4.0
in solid phase 2.3 4.5
weight loss after 10 days at 280C, % 5.7 6.6
Dielectrieal constant (1000 c/s) at 20C 3.02
150C 3.06
220C 3.14
tg S (1000 c/s) at 20C 0.3 x 10 2
150C 0.5 x 10-2
220C 1.1 x 10-2
EXAMPLE VI
A pre-polymerized mixture of Poly-isoeyanate 30 (2 parts by weight)
and styrene (1 part by weight) was prepared by mixing the components, and
adding 1.5 ~w of a eatalyst mixture contaiing 10 ~w of benzyl trimethyl
- 12 -
lU37639
ammonium hydroxide, 15 ~w o~ methanol, and 75 ~w of benzyl alcohol withvigorous stirring within a few minutes. The resulting mixture was cooled
down and kept at ambient temperature during 16 hours; then 0.2 %w of benzoyl
chloride was added to inhibit further reaction~ The viscosity (initially
0.06 poise at 25C) was now 2.7 poises at 25C, and remained on the same
level after storage during 14 days at ambient temperature.
~XAMPLE VII
Pre-polymerized mixtures were prepared as follows:
In a reactor of 2 l pro~ided with baffles and stirrer poly:iso-
cyanate 30 (1000 g) and styrene (100 g) were mixed, and a mixture of styrene
(300 g), benzyl trimethyl ammonium hydroxide (2.1 g)~ methanol ~l5 g)~ and
benzyl alcohol (15.75 g) was added with stirring (500 rotations per minute)
in 3 minutes at ambient temperature. After 1 minute further stirring the
liquid was sieved through a fine metal sieve (200 mesh), and parts of it
were used for the following pre-polymerization and stopping experiments:
(a) heated to 75C, and kept at 75C during 30 ~inutes; then 0.1
~w of benzoyl chloride was added.
(b) kept at 25C during 16 hours; then 0.2 %w of benzoyl chloride
was added.
(c) kept at 25C during 16 hours; then 0.4 ~w of chloranil was
added.
The storage stability of the mixtures (a), (b) and (c) was deter-
mined by keeping the mixture at 75C during the time indicated in Table IV
and measuring the viscosity at 25C.
Table IV
Resin from Viscosity (poise_at 25C)
experiment initia1 after beir~ kept at ?5C during
1 day 2 days 13 days 20 days
_
a 3.7 4.0 4.0 5.0
b 1.7 1.7 2.0 2.0 2.2
c 1.7 2.3 2.5 3.4 4.3
- 13 -
1~37~ 9
The mixture without benzoyl chloride or chloranil formed a gel
when kept at 75C during 1 day.
Castings and laminates were prepared from the prepolymerized resins
(a), (b) and (c) by adding 2 ~w DMP-30 as catalyst and 4 ~w Polyether A as
co-catalyst, and curing 16 hours at 25C and subsequently 3 hours at 200C.
_ AMPLE VIII
A prepolymerized mixture of polyisocyanate 30 (10 parts by weight)
and styrene (4 parts by weight) was prepared by mixing the components and
adding 2.4 ~w lbased on total weight of polyisocyanate and styrene) of a
mixture of 90 ~w of Polyether A, 5 ~w of triethylene diamine, and 5 ~w of
benzyl alcohol; the resulting mixture was kept at 50C during 1 hour, ~
and cooled to 25C, then 0.2 ~M of benzoyl chloride was added to stop further
reaction. The viscosity was now 3.0 poises at 25C; it increased to 5 poise
at 25C a~ter storage during 20 days at ambient temperature. Castings were
prepared f~om the prepolymerized mixture as in Example VII.
- 14 _
