Note: Descriptions are shown in the official language in which they were submitted.
o.z. oo50/~;~9~34O
Prepreg for hiqh performance com~oqite materials
The pre~ent invention relates to a prepreg for
high performance compoqito materialq which i8 curable by
a free radical reaction and is composed of an essentially
monomer-freo vinyl ester urethane re~in and oriented
reinfor~ing fiber3.
High performance compo~ite ma~erial~ are increa~-
ingly used in the aircrsft and automotive vehicle indu~-
tries. ~ighly stres~ed partq quch aq leaf springs are
already being produced on an indu~trial ~cale from
prepregs baqed sn epoxy ro~in~ and oriented glaR3 fiber
bundles. Apart from thair high price, however, epoxy
re4ins have the diQadvanta~e of comparatively long curing
cycles; al~o, the cured compo~ite~ have an un~atis
factorily high moi~ture regain.
It i~ an ob~ect of the pre~nt invention to
provide a prepreg for high performancQ compo ite mater-
ia7~ which i8 free of the disadvanta~es mentioned.
W~ hava found that this ob~ect is achieved by a
prepreg compo~ed of oriented reinforcing fiber~ and
essentially monomer-free vinyl e~ter ure~hane resins.
The present invention accor~ingly provides a
prepreg for high performance composite material~ which i~
curable by a free radical re~ction, con~aining from 30 to
70 ~ by volum~ of oriented reinforcing fibax~ and from 70
to 30 ~ by volume of a vinyl ester urethans resin pre-
pared by reacting
~) a polyi~ocyanate,
with or without
Bl) a diamin~ or
B2) a dihydric alcohol and
C) a hydroxyalkyl (meth)ac~.~late,
in a weight ratio of As~Bl+B2) of from 100:0 to 100:30,
preferably from 1nos5 to 100:15, the resin containing not
more th~n l % by weight of free i~ocyanate groupY.
According to the invention, the vinyl e~ter urethane
;2 ~3~
- 2 - o.z. 0050/41557
resin contains les~ than 2 % by weight of unsaturated
monomer~.
Monomer-containing vinyl est~r urethanes have
been known for a long tLme, for example from
US-A-3 297 745 and US-A-3 772 404. US-A-4 390 662
describes mixture~ of un~aturated polyester~ with from
O.5 to 70 % by weight of an acrylic urethane based on a
long-chain polyesterpolyol or polyethexpolyol, which may
also be monomer-free. Such re~ins are not suitable for
producing hi~h performance compositz materials, since,
owing to the high level of unsaturated polyester, the
mechanical propertie~, in particular the heat resistance
and the ~trength of the moldings, would be much too low.
US-A-4 131 602 describe~ the reaction of a triol
or tetraol with a diisocyanate and a subsequent reaction
with a hydroxyacrylate. The reaction product can be used
as a radiation-curable coating agent.
VS-A-4 213 857 de~cribes the reaction products of
bisphenol Atpolyester polyol with a polyi~ocyanate and a
hydroxyl-terminated acrylic estQr. ThesQ vinyl ester
urethanes, di~solved in copolymerizable ~olvents, are
used a coating agents.
EPoA-64 809 describes a proces for producing a
plastic moldin~ wherein a fluent solution of a poly-
urethane-polyacrylate re~in in monomeric methyl methacry
late i8 in~ected into a mold. Apart from the fact that
thl~ mixtux~ contai.n~ large amount~ of a low-boiling
monomer, it would not be suitable for Lmpregnating
oriented reinforcing fibers and hence for producing high
performance compo~ite materials on account of its low
vis~osity.
DE-A-37 44 390 des~ribes compo~i~e material~
formed from reinforcing fiber3 and a modified vinyl ester
urethane resLn which has a ~:umilar structure ~o the resin
of the present invention. Where it differ~ significantly
from the latter is that it is pres2n~ in solution in at
least 15 % by weight of un~aturated monomsrs, preferably
2039~340
- 3 - o.z. 0050/41557
instyrene. Such low-vi~cosity resins are highly suitable
for Lmpre~nating the loose fiber mat~ which are preferred
as reinforcing fiber~ in said DE-A-37 44 390. For Lmpreg-
nating oriented reinforcing fiber~ of the type required
S in prepregs for high performance composite materials and
for the further proces~ing of the prepreg, however, their
vi~co~ity would be much too low. Moreover, the styrene,
because of its high vapor pressure, would pra~ent a
problem in the processing of the prepreg by the autoclave
method.
The following remarks concern tha starting
material:
Reinforcing fiber
Suitable reinforcing fibers are customary inor-
ganic or organic fibers, preferably those made of gla~R,carbon or aromatic polyamide. The e~Yential a~pect is
that the fiber~ are oriented. Fiber m~t~ are thuR not
suitable. Preference i~ given to laid fiber~, in par-
ticular unidir~ctionally oriant0d gla88 fibers, and to
woven fibars. The prepregs of the present invention
contain ~rom 30 to 70, preferably from 50 to 60, % ~y
volume of reinforcing fiber3.
IRocyanato~
To prepare tho vinyl e.~ter urethane resins for
the purpos~s o~ the present in~an~ion it i8 possibl~ to
u8e any ~nown aliphatic, cycoaliphatic or aromatic
polyisocyanAte havin~ at least 2 isocyanate groups per
molaculeO E~camples of ~uitable isocyanate~ are:
4,4-diphenyLmethan~ diisocyanate (MDI), hexamethylene
dii~ocyanate (HDI), trimethylhexyl diisocyanata ( TMDI ),
cyclohexyl diisocyanate, dicyclopenta~ienedimethylena
diisocyanate, diisocyanatodiphenyl ether, diiqocyanato-
naphthalene, diphenylmethane diisocyanate and diisocyana-
totoluene with t.heir isomer mixture~, isophorone
dii30cyan~te (IPDI), dicyclohexyl diisocyanate, poly-
phenylenepolymethylene polyisocyanates ~crude MDI);
triisocyanatocyclohexane, trii~ocyanatotoluene,
;~39~40
- 4 - O.Z. 0050/41557
triisocyanatonaphthalene, triisiocyanatobiphenyl, tri-
isocyanatotrLmethylbenzenQ, trii~iocyanotodiphenylmethane,
triisocyanatomethyldiphenylmethane, triisocyanatotri-
phenylmethane, triiqiocyanatodiphenyl ether, tetraiso-
cyanatodiphenyl sulfide; urethane-containing prepolymeric
polyisiocyanates siuch a~ the reaction product of trimethy-
lolpropane and diiqiocyan~otoluene; trLmerized polyiso-
cyanate~i which contain isocyanurate groups and are hased
for example on HDI t diphenylmethane diisiocyanatQ and
isophoronQ diisiscyanate; prepolymeric polyisocyanateq
prepared by reaction of polyisiocyanate~i with A deficiency
of polyepoxide~i in th~ pre~3ienca of suitable cataly3tsi;
polyisiocyanatesi which by prereaction of ~iome of the NCO
groupsi contain earbodiLmide and urethoneLminQ units; and
also prepolymersi which contain not only NCO group~ but
urethdione unitq.
Preferred isiQcyanates are 4,4'-diphenylmethane
diisocyanate and the isom~r mixture of 2,2'- a~d 4,4'-
diphenylmethane diisocyanate.
Diamines
Suitable diamines includ~ not only aliphatic
amine~i but al~io aromatic amine~i. Example~ are: ethylene-
diamine, diethylenetriamine, bi~(4-aminocyclohexyl)meth-
ane, diaminodiphenylmethane and diaminodiphenyl ~3iulfone.
Particularly suitable aminas are long-chain amines having
molecular weights of from 150 to 5000. Thsy include ether
diam~ne~ ~3iuch 28 4,7-dioxadecRne-1,10diamine and com-
pound~ of the general formula
H2N (C3H60)m-C3H6-NH2,
where m i9 from 2 to 80, or cempounds of the general
formula
H 2N-C 3H6 ~0- [ ( CH 2 ) 4] n -C 3H6 -NH 2,
where n isi from 5 to 80; alsio the aminobenzoic estersii and
~039l~4~)
- 5 - O.Z. OOS0/41557
anthranilic e~ter~ of diol~ ~uch a~ ethylenQ glycol,
propylene glycol, polyethylene glycol, polypropylene
glycol, p~lybutadiene glycol, polycaprolactone glycol or
polytetramethylene ether glycol. The particularly pre-
ferred aminobenzoic est2r~ of polytetramQthylene etherglycol have the following structure:
H2~ C02--C4H90--r (CH2) 40] -C4~18-02C~ NH2
where p i8 from S to 80.
Dihydric alcohol~
E~ample~ of dihydric alcohols which are quitable
for reaction with i~ocyanate~ are: aliphatic diol~ or
polyetherol~, preferably those having a molecular weight
of le~ than 750, in particular le~ than 600, such a3
1,2 ethanediol, 1,2-propanediol, 1,4-butanediol, dipropy-
lene glycol, neopentylglycol, and alAo polyethylene
glycol and polypropylene glycol, or alicyclic diol~, such
a hydrogsnated bisphenol A, cyclohexanediol, cyclo-
hexanedimethanol and tricyclohexanedLmethanol, also
phenols such as bisphenol A or re~orcinol, and also
alko~ylated derivatives of bi~phenol~ such a~
bisphenol A, bisphenol S or bi3phenol P. In principle it
i~ al~o possible to reaet the isocyanate~ with aminol~
quch as ethanolamine, propanolamine, diethanolamine,
triethanol~mine and aminophanol~. Preferance i~ given to
dipropylsne glycol with or without polypropylene glycol.
Hydroxyalkyl (meth)acrylates
To incorporate the terminal double bonds into
vinyl ester urethane, hydroxyalkyl (meth)acrylateR are
reacted with the i~ocyanate cempounds prepared from A, B1
and B2. Hydroxyalkyl (meth)ac~rrlate~ ~r~ de~cribed by the
following general formulas
C H 2=C--C0 2--R --OH
2()39~
- 6 - o.z. 0050/41557
where R i~ hydrogen or methyl
and R' is alkylene of 2 or 3 carbon atom~. Hydroxyalkyl
(meth)acrylates are prepared by reacting (meth)acrylic
acid with alkylene oxide~ ~uch a~ ~thylene oxide or
propylene oxide. Suitable hydroxyalkyl (meth)acrylates
for th~ purpose~ of the present invention also include
glycerol (dLmeth)acrylates, trLmethylolpropane (dimeth)-
acrylate~ and pentaerythritol (trLmeth)acrylates, with
hydroxypropyl (meth)acrylate and hydroxyethyl (meth)-
acrylate being preferred.Monomers
According to the present invention, the vinyl
ester urethane resin contains less than 2, preferably
le~ than l, % by weight of monomer~ having a boiling
point above 200C (at 1013 mbar). These may be added for
specifically adjusting the vi~cosity, in which ca~e the
preference i~ for di(meth)acrylate~ of diols or poly-
etherol~, low molecular weight maleimide~ such as
N-phenylmaleLmide/ N-alkylmaleimides and N-cyclohexyl-
maleLmide~, and diallyl phthalate. The e~sential require-
ment i3 that the resin shall be vlrtually free of
monomer~ having a lower boiling point, in particular that
the re~in~ ~hall be free of styrene.
The vinyl e~ter urethane re~in3 used according to
the present invention ~hould have a comparatively high
vi3cosity. The melt vi8c08ity, measured at 100C using an
Epprecht plate/cone vi~cometer, should preferably be
above 50 mPa~, in particular within the range from ~00 to
2500 ~Pas. I~ the vi co~ity i3 too low, tho re~in will
flow out of the prepreg at room temperature; if the
viscosity i~ too high, there is a danger of fiber~
breaking as thay are being impregnated. The mo~t 4uitable
viscosLty can be ~et throush appropriate choica of the
molecular weight of the re~in (ad~u~table via the diols
or diamine4) or by adding th~rmoplastic~ or rubbers which
may carry reactive groupC (for example COOH, OH or NH2
group~). The vi~cosity can al~o be influenced by the
~9~o
- 7 - o.Z. 0050~41557
addition of small amounts of monomer~.
To speed up the reactions of the isocyanates ~ith
the alcohol and amino compound~ i~ is possible to use
suitable cat~lyst~ as known from polyurethane chemistry.
S They include for exampla tertiary amines such as
1,2-dLmethylLmidazole, diazabicyclooctane, diazabi-
cyclononane, triethylenediamine, metal salts such as lead
octoate, tin octoate or dibutyltin dilaurate and also
mixtures of tertiary amine~ and metal salts. The3e
catalyst~ are cu~tomarily added in amoun~ of from 0.05
to 2 ~ by weight, ba~ed on A + B + C.
Pr~mature gelation of the reaction mixture can be
prevented by the addition of customary inhibitors, eg.
phenothiazine, hydroquinone, dimethylhydroquinone,
trLmethylhydroquinons~ tertbutylhydroquinone, hydro-
quinone monomethyl ether, tert-butylpyrocatechol,
triphenyl phosphite or p-benzoquinone. The inhibitor~ are
added in amounts of from 0.01 to 2 % by weight, based on
A + B ~ C.
To prepare tho modified vinyl ester urethane
re~in~ there aro various options. Pir~t, the i~acyanate A
can b~ prereacted with a portion of ~he hydroxyalkyl
(meth)acrylate C in a molar ratio of about 1:0.5-1:1.5
and then with the polyhydric alcohol B2 and/or the poly-
amine Bl, theraaftar the free NCO groups are reacted with
the remaining hydroxyalkyl (meth)acrylate. Secondly, by
mixing the components A, Bl and any ~2 in a ratio of
A:(Bl+B2) of from 100:0 to 100:30 and re~cting at 40-
110C before adding the amount of hydroxyalkyl (meth)-
acrylate C required for ~aturating the freu isocyanate
groups. Thirdly, by reacting the component~ A, ~1, B2 and
C together in a ono-pot reaction to glve the vinyl ester
urethane resin. Any exce~ polyisocyanate present reacts
with thQ hydroxyalkyl (me~h)acrylat6 to give a low
molecular w~ight vinyl e~ter urothane which may be
utilized for ad~usting the ~iSc08ity of the re~in. The
product obtained at all times i8 a mixture of
2~)35~8~
- 8 o.Z~ 0050/41557
prepolymeric vinyle~terurethanes which differ in chain
length and molecular weight. In principle it is also
possible ~o U5e the sLmple reaction product of 2 mol of
hydro~yalkyl (meth)acrylate with 1 mol of diosocyanate.
S The vinyl ester urethane resin may be admixed
with amounts of from 2 to 20 % of it~ weight of other
curable resins, such as vinyl ester, bismaleLmide or
epoxy re ins. To Lmprove it~ toughne~ the vinyl eqter
urethane resin may contain from 2 to 20 % of i~ weight
of a thermoplastic, such a~ polyamide, polye~ter or
polyether sulfone, or of a rubber.
Tha vinyl ester urethane resin~ are combined with
reinforcing fiber~ by the preprag technique. This tech-
nique i~ described for example in US-A-3 784 433. First
a vinyl ester urethane re3in film i~ prepared, preferably
with a sheet weight of from 10 to 400 g-m~2, and ~he
a~sembly of reinforcing fiber i8 laid on top of thi~
film, po~sibly with another re~in film on top. The layers
are calendsred together at 50-150~C and 1-10 bar to give
a prepreg.
These prepregq can be draped on top of one
another in a plurality of plieR and then molded ~ogether
and ~ub~ected to fres radical curing in a conventional
manner. To this end, the prepregs are cut to si2e and
draped on top of one another in a parallel arrangement or
oriented at various angles. The curing then takes place
either in an autoclave at from 2 to 10 bar or in a pre~s
at from 10 to 100 bar. In either case the temperature is
within the range from 80 to 200C.
To cure the vinyl ester urethane resins it i5
possible to U~Q customary polymerlzation initiators,
which are added to the resin in amounts of from 0.1 to
10 % by weight, preferably from 0.5 to 3 % by weight.
Suitable free radical initiators are for example: benzoyl
peroxid~, tert-butyl peroctoate, tert-butyl per~
benzoate, tert-butyl peroxide, dicumyl peroxide, tert-
butyl cumyl peroxide, di(4-methylbenzoyl)peroxide,
~039~34~)
- 9 _ o.z. 0050/41557
di(tert-hutyl)peroxide and orqanic compound~ having a
labile carbon-carbon bond. If cu~tomary photoinitiators,
eg. henzoin ether~, benzil ketals or acylphosphine
compound~, are u~ed, ths curing may alternatively be
carri~d out by irradiation wLth light of wavelength
200-50 nm.
The prepregs of the pre~ent invention can be used
to produce high performance composite materials, for
example aircraft part~, eg. aileron~ and fuselage shells,
automobile part~, machine parts or sports article~, eg.
tennis rackets or fi~hing rod3~
The present invention further provides high
performance compoxit~ materialc containing frsm 30 to
70 % ~y volume of oriented glass fiber and from 70 ~o
30 % by ~olume of a cured vinyl e~ter urethane resin
which contain~ virtually no copolymerized ~tyrene units,
which are defined by the following propertieY: an inter-
laminar hear ~trength ILS, maasured in accordance with
Sacma S~andard SR~ 4-88, of greater than 90, preferably
greater than 100 [MPa], a 90 ten9il2 strength, measured
in accordanc with Sacma Standard SR~ 8~88, of greater
than 50, preforably greater than 70 [MPa], and a glass
transition temperature Tg of more than 130C, preferably
more than l50~C.
E~AMPLES
A. Preparation of vinyl estar urethane resin
1. 300 g of the isomer m$xture of diphenylmethane
diisocyanate ara admixed with 1 ml of dibutyltin
dilau~ate, and 157 g of hydroxypropyl methacrylate are
added dropwi~e a~ 40C. ~hen 15 g of dipropylene glycol
are added, the remaining isocyanate groups are reacted
with a further 157 g of hydroxypropyl methacrylata, and
the reaction mixture i8 ~u,bsequently stirred at 80C
until tha residual isocyanate content ha~ dropped to
belsw 0.1 %, at which point 0.61 g of dicumyl peroxide
and 200 ppm of phenolic inhibLtor are s~irred into the
resin (visco~ity 390 mPah at 100C).
~035~840
- .L0 - O.Z. 0050/41557
2. 325 g of a prepolymeric diisocyanate based on 282 g
of 4,4'-diphenylmethane diisocyana~a, 27.1 g of dipro-
pylene glycol and 15.9 g of polypropylene glycol (MW 450)
are admixed with 1 ml of dibutyltin dilaurate ~nd reacted
at 40C with 260 g of hydroxypropyl methacrylate. The
mixture is then stirred at 90C for 1 h, catalyzed with
0.58 g of dicumyl peroxide and inhibited with 200 ppm of
a phenol. The vi~co~ity of the re~in at 100C is
1700 mPas.
3. 2,530 g of the i~omer mixture of diphenylmethane
diisocyanate are admixed with 2 ml of dibutyltin
diluarate and reacted at 40C with 940 g of bis(para-
aminobenzoic ester)polytetrahydrofuran 650. Thereafter
2,760 g of hydroxypropyl (meth)acrylate are added at
50C, and the mixture i~ heated to 70C and stirred at
that temperature for 1 hour. The re~in i5 admixed with
400 ppm of dimethylhdyroquinone and 31.3 g of dicumyl
peroxide. The resin has a melt viscosity (100C) of
480 mPa~.
4. 3,006 g of the i~omer mixture of diphenylme~hane
diixocyanate are admixad with 195 g of a rubber based on
acrylate (Paraloid E~L 2600) and 3.5 ml of dibutyotin
dilaurate and reacted at 40-50~C wi~h 1,572 g of hydroxy-
propyl (meth)acrylate. Then 151 g of dipropylena glycol
ar~ added at thst temperature, followed by a further
1,572 ~ of h~droxypropyl (meth)acrylate. This is in turn
followad by 3 ml of dibutyltin dilaurate, 6.3 g of
phenothiazine and 6.3 g of triphenyl phosphite, heating
to 80-C and stirring at that temperature for 1 hour. The
mixtur~ i~ then cooled down to 70 and admixed with 63 g
of dicumyl peroxido,The re~in has a vi~cosity of 340 mPas
(cone/plate viscosity at 100C).
Hl. Prepar~tion of prepreg with gla~s fibres
The vinyl ester ure~hane resins are first applied
with a laboratory coater to ~iliconized paper in a film
w~igh~ of 140 g.m~2 by the method of contrarotation and
the U8Q of a nip. The film i8 then covered with a sheet
2;0~989~
~ O.Z. 0050/41557
of polyethylenQ and wound up.
Parallel gla~s fiber roving~ (PPG 1062-247) are
then pres~ed in a sheet weight of 560 g m 2 into the re~in
film by the two-film technique using three calender~ at
60-140C and 1-8 bar. In the course of the calendering
the resin film become attached to the laid rovings. The
prepreg i~ then covered with ~iliconized paper and a
~heet of polyethylene, rollad up and ~tored. The shee~
weight of the prepreg is 840 g m~2.
B2. Prepregs with carbon fiber~
~he resin film (sheet weight 70 g m~2) i~ molded
by the ingle-film technique with parallel carbon fiber
roving~ (Celion G 30-S00) having a sheet waight of
140 g m~2. The prepreg ~heet weight i8 210 g-m~2 and the
- 15 re~in content i~ 33 % by weight.
C. Production of a composite material
The prepreg~ are trlmmed in size to 30x3G cm, and
6 ~uch cut~ are then draped on top of one another unidir-
ectionally and cured in an autoclave. The prassure i~
6 bar, and the tempera~ure i~ rai~ed from 30 to 190C in
the course of 8 h.
The laminate havo the properties indicated in
the table. For comp~rison the table al~o include~ a
laminat~ based on a convention~l epoxy resin (mixture of
tetraglycidyldiaminodiFhenylm~thane + bisphenol A epoxide
+ novol2k epoxide + dicyandiamide).
TABLE
Resin Al A2 A3 A4 Epoxy Al
F1bers B1 B1 B1 B1 B1 s2
. _
ILS (dry, 23C) [MPa] 119 11696 108 34 116
Tensile ~trength [~IPa] 84 79 76 - 75
Tg [ C] 181 1132175 186185 178
