Method for preparing fiber-reinforced parts based on cyanate ester/epoxy blends
Field of the Invention
The invention relates to a method for preparing fiber-reinforced parts based on cyanate
ester/epoxy blends and to fiber-reinforced parts obtainable by said method.
Background of the Invention
There are several established methods for the production of fiber-reinforced parts based
on thermoset resins. Newer methods, such as resin infusion, resin injection, filament
winding, pultrusion and compression molding and further variants hereof can be
technically and economically more efficient than the traditional prepregging. See e. g .
Flake C. Campbell, Jr., Manufacturing Processes for Advanced Composites, Elsevier
Ltd. 2004, ISBN 978-1-8561 7-41 5-2. These methods allow the utilization of carbon fiber
reinforced plastic (CFRP) molds for the manufacturing of high performance composite
materials. For small part production volumes, CFRP molds are much cheaper than steel
or invar tooling. Invar tooling is usually required to provide beneficial thermal expansion
to manufacture dimensionally stable materials. CFRP molds offer a thermal expansion
coefficient similar to that of the parts manufactured using these molds, which eventually
leads to better dimensional accuracy (Campbell, pp. 104-1 10, 336).
Today those materials generally are manufactured with prepreg materials, mainly based
on carbon fiber reinforced epoxy resin systems. However, it is getting more and more
common to utilize liquid epoxy resins systems for manufacturing CFRP molds by
infusion, in some cases to utilize the same resin systems for mold manufacturing and
for manufacturing the molded parts. Due to the curing cycles molds are thermally
stressed, which results in decreasing interlaminar shear strength (ILSS) values of
epoxy-based CFRP molds. It was therefore an object of the invention to provide a
method for producing fiber-reinforced parts, such as CFRP molds, that withstand
thermal stress for a long period of time without deteriorating their mechanical properties.
US 201 1/01 39496 A 1 discloses resin compositions comprising a cyanate ester resin
and a naphthylene ether type epoxy resin and, optionally, a curing accelerator. The
cyanate ester resin content is preferably not more than 50% by mass. The resin
compositions are used to produce adhesive films from solutions in solvents such as
methyl ethyl ketone or solvent naphtha and the curing accelerators used include metal
compounds such as zinc naphthenate or cobalt acetylacetonate. US 201 1/01 39496 A 1
further mentions that its resin compositions could also be used to prepare prepregs, but
such process would require either a solvent or high temperatures ("hot melt method").
WO 2013/074259 A 1 discloses polycyanate ester compositions containing silica
nanoparticles. The preparation of the compositions involves a step wherein the
polycyanate ester and the nanoparticles are dissolved or dispersed in a solvent, and a
subsequent distillation in a wiped film evaporator. Even the solutions/dispersions before
the distillation have a high viscosity of between about 10 Pa*s ( 10,000 mPaxs) and
about 250 Paxs at 72 °C.
WO 2006/034830 A 1 discloses a two-step process for the solvent-free preparation of a
fiber-reinforced resin-coated sheet. In the first step a powdered resin, such as a (solid)
cyanate ester or epoxy resin is applied to a substrate selected from a woven or nonwoven
fabric using magnetic and electrostatic forces, and in the second the thus
obtained layer of coating powder is molted and cured. The process requires a system of
magnetic and/or electrically charged rolls and it appears to be applicable to flat and
preferably continuous substrates only.
Summary of the Invention
The invention provides a method for producing time-efficiently - meaning fast curing -
fiber-reinforced parts based on cyanate esters or cyanate ester/epoxy blends using
methods like resin transfer molding, vacuum assisted resin transfer molding, liquid resin
infusion, Seemann Composites Resin Infusion Molding Process, vacuum assisted resin
infusion, injection molding, compression molding, spray molding, laminating, filament
winding, and pultrusion with a potentially high temperature resistance. With the
formulations and the process parameters according to the invention it is possible to
manufacture high-performing fiber reinforced composite parts as far as temperature
resistance, mechanical properties and other characteristics are concerned.
Detailed Description of the Invention
According to the invention, a fiber-reinforced part based on cyanate ester or a cyanate
ester/epoxy blend is prepared by a method comprising the steps of
(i) providing a liquid mixture comprising
(a) from 15 to 99.9 wt.% of at least one di- or polyfunctional cyanate ester
selected from the group consisting of difunctional cyanate esters of formula
wherein R1 through R4 are independently selected from the group consisting
of hydrogen, linear C1-10 alkyl, halogenated linear C1-10 alkyl, branched C4_io
alkyl, halogenated branched C4_io alkyl, C3-8 cycloalkyl, halogenated C3-8
cycloalkyl, C1-10 alkoxy, halogen, phenyl and phenoxy,
difunctional cyanate esters of formula
(lb)
wherein R5 through R12 are independently selected from the group consisting
of hydrogen, linear C1-10 alkyl, halogenated linear C1-10 alkyl, branched C4_io
alkyl, halogenated branched C4_io alkyl, C3-8 cycloalkyl, halogenated C3-8
cycloalkyl, C1-10 alkoxy, halogen, phenyl and phenoxy;
and Z1 indicates a direct bond or a divalent moiety selected from the group
consisting of -O-, -S-, -S(=0)-, -S(=0) 2- , -CH(CF 3)-, -C(CF 3)2- ,
-C(=O)-, -C(=CH 2)-, -C(=CCI 2)-, -Si(CH 3) - , linear C1-1 0 alkanediyl,
branched C4_io alkanediyl, C3-8 cycloalkanediyl, 1,2-phenylene,
1,3-phenylene, 1,4-phenylene, -N(R 13)- wherein R13 is selected from the
group consisting of hydrogen, linear C1-10 alkyl, halogenated linear C1-1 0
alkyl, branched C4_io alkyl, halogenated branched C4_io alkyl, C3-8 cycloalkyl,
phenyl and phenoxy, and moieties of formulas
(lc)
and oligomeric mixtures thereof, wherein n is an integer from 1 to 20 and R14
and R15 are independently selected from the group consisting of hydrogen,
linear Ci_io alkyl and branched C 4-10 alkyl;
(b) from 0 to 84.9 wt.% of at least one di- or polyfunctional epoxy resin selected
from the group consisting of epoxy resins of formula
wherein Q1 and Q2 are independently oxygen or - N(G)- with
G = oxiranylmethyl, and R16 through R19 are independently selected from the
group consisting of hydrogen, linear C1-10 alkyl, halogenated linear C1-1 0
alkyl, branched C 4-10 alkyl, halogenated branched C 4-10 alkyl, C3-8 cycloalkyl,
halogenated C3-8 cycloalkyl, C1-1 0 alkoxy, halogen, phenyl and phenoxy;
epoxy resins of formula
wherein Q3 and Q4 are independently oxygen or -N(G)- with G = oxiranylmethyl,
R20 through R27 are independently selected from the group consisting
of hydrogen, linear Ci_io alkyl, halogenated linear Ci_io alkyl, branched C4_io
alkyl, halogenated branched C4_io alkyl, C3-8 cycloalkyl, halogenated C3-8
cycloalkyl, C1-1 0 alkoxy, halogen, phenyl and phenoxy, and Z2 indicates a
direct bond or a divalent moiety selected from the group consisting of -O-,
-S-, -S(=O)-, -S(=0) 2- -CH(CF 3)-, -C(CF 3)2- , -C(=0)-, -C(=CH 2)-,
-C(=CCl2)-, -Si(CH 3)2_ , linear C1-1 0 alkanediyl, branched C4_io alkanediyl,
C3-8 cycloalkanediyl, 1,2-phenylene, 1,3-phenylene, 1,4-phenylene,
glycidyloxyphenylmethylene and -N(R 28)- wherein R28 is selected from the
group consisting of hydrogen, linear C1-10 alkyl, halogenated linear C1-1 0
alkyl, branched C4_io alkyl, halogenated branched C4_io alkyl, C3-8 cycloalkyl,
phenyl and phenoxy;
epoxy resins of formula
( l ie)
and oligomeric mixtures thereof, wherein m is an integer from 1 to 20, Q5 is
oxygen or -N(G)- with G = oxiranylmethyl, and R29 and R30 are
independently selected from the group consisting of hydrogen, linear Ci_io
alkyl and branched C4_io alkyl; and naphthalenediol diglycidyl ethers;
and
(c) from 0.1 to 25 wt.% of a metal-free catalyst;
(ii) providing a fiber structure
(iii) placing said fiber structure in a mold or on a substrate,
(iv) impregnating said fiber structure with said liquid mixture, optionally by applying
elevated pressure and/or evacuating the air from the mold and fiber structure, at a
temperature of 20 to 80 °C, and
(v) curing said liquid mixture by applying a temperature of 30 to 150 °C for a time
sufficient to cure said mixture.
The expression "liquid mixture" means a mixture that is liquid at ambient temperature
(typically about 25 °C) and has a viscosity of preferably less than 10,000 mPaxs at
ambient temperature and preferably less than 1,000 mPaxs, more preferably less than
500 mPaxs, and most preferably no more than about 300 mPaxs at a temperature of
80 °C or less.
Here and hereinbelow, the expression "linear Ci_io alkyl" includes all alkyl groups
having 1 to 10 carbon atoms in an unbranched chain, irrespective of their point of
attachment. Examples of Ci_io alkyl groups are methyl, ethyl, 1-propyl, 2-propyl
(isopropyl), 1-butyl (n-butyl), 2-butyl (sec-butyl), 1-pentyl, 2-pentyl, 3-pentyl, 1-hexyl,
2-hexyl, 3-hexyl and so on. Especially preferred linear Ci_io alkyl groups are methyl,
ethyl, 1-propyl, 2-propyl (isopropyl) and 1-butyl (n-butyl). Similarly, the expression
"branched C4-io alkyl" includes all alkyl groups having 4 to 10 carbon atoms and at least
one branching point. Examples of branched C4_io alkyl groups are 2-methyl-1 -propyl
(isobutyl), 2-methyl-2-propyl (terf-butyl), 3-methyl-1 -butyl (isopentyl), 1,1-dimethyl-
1-propyl (terf-pentyl), 2,2-dimethyl-1 -propyl (neopentyl) and so on. Especially preferred
branched C4_io alkyl groups are 2-methyl-1 -propyl (isobutyl) and 2-methyl-2-propyl (tertbutyl).
The expression _4 alkyl" includes methyl, ethyl, 1-propyl, 2-propyl (isopropyl),
1-butyl, 2-butyl (sec-butyl), 2-methylpropyl (isobutyl), and 2-methyl-2-propyl (terf-butyl)
while the expressions C _4 alkoxy" and C _4 alkylthio" include the before mentioned
Ci 4 alkyl groups bound via an oxygen or divalent sulfur atom. Particularly preferred
"Ci_4 alkoxy" and "Ci_4 alkylthio" goups are methoxy and methylthio. The expression
"C3-8 cycloalkyl" includes saturated carbocyclic rings having 3 to 8 carbon atoms, in
particular cyclopropyl, cyclobutyl, cyclopentyl, cycloheptyl and cyclooctyl. Especially
preferred C3-8 cycloalkyls are cyclopentyl, cyclohexyl and cycloheptyl.
The expressions "halogenated Ci_io alkyl", "halogenated branched C4_io alkyl" and
"halogenated C3-8 cycloalkyl" include any of the beforementioned groups bearing one or
more halogen atoms selected from fluorine, chlorine, bromine and iodine at any position
of the carbon chain or ring. Two or more halogen atoms may be equal or different.
The expression "Ci_io alkoxy" includes any of the beforementioned linear Ci_i o alkyl or
branched C4_io alkyl groups bound via an oxygen atom in an ether linkage, such as
methoxy, ethoxy, 1-propoxy, 2-propoxy (isopropoxy), 1-butoxy and so on.
As mentioned above, the expression "halogen" includes fluorine, chlorine, bromine and
iodine.
The expressions "linear C1-10 alkanediyl", "branched C4_io alkanediyl" and "C3-8
cycloalkanediyl" include unbranched Ci_i o alkane chains, branched C4_io alkane chains
and saturated carbocyclic rings having 3 to 8 carbon atoms, respectively, according to
the above definitions of "linear C1-10 alkyl", "branched C4-10 alkyl" and "C3-8 cycloalkyl",
having two open valencies at the same or different carbon atom(s). Examples of linear
C1-10 alkanediyl groups are methanediyl (methylene), 1,1-ethanediyl (ethylidene),
1,2-ethanediyl (ethylene), 1,3-propanediyl, 1,1 -propanediyl (propylidene), 2,2-propanediyl
(isopropylidene), 1,4-butanediyl, 1,5-pentanediyl, 1,6-hexanediyl and so on.
Examples of branched C4_io alkanediyl groups are 2-methyl-1 , 1 -propanediyl (isobutylidene),
2-methyl-1 ,3-propanediyl and 2,2-dimethyl-1 ,3-propanediyl. Examples of
C3-8 cycloalkanediyl groups are 1, 1 -cyclopropanediyl, 1,2-cyclopropanediyl, 1,1-cyclobutanediyl,
1,2-cyclobutanediyl, 1,3-cyclobutanediyl, 1, 1 -cyclopentanediyl, 1,2-cyclopentanediyl,
1,3-cyclopentanediyl, 1, 1 -cyclohexanediyl, 1,2-cyclohexanediyl, 1,3-cyclohexanediyl
and 1,4-cyclohexanediyl. Cycloalkanediyl groups having the open valencies
on different carbon atoms may occur in cis and trans isomeric forms.
Naphthalenediol diglycidyl ethers include the diglycidyl ethers of any naphthalenediol,
such as 1,2-naphthalenediol, 1,3-naphthalenediol, 1,4-naphthalenediol, 1,5-naphthalenediol,
1,6-naphthalenediol, 1,7-naphthalenediol, 1,8-naphthalenediol, 2,3-naphthalenediol,
2,6-naphthalenediol and 2,7-naphthalenediol. Preferred are the diglycidyl
ethers of the symmetric naphthalenediols, i.e., the 1,4-, 1,5-, 1,8-, 2,3-, 2,6- and
2,7-naphthalenediols. Especially preferred is the 2,6-naphthalenediol diglycidyl ether.
The polyfunctional cyanate esters (Ic) and polyfunctional epoxy resins (lie) may be
oligomeric mixtures of molecules having different values of n . Such oligomeric mixtures
are usually characterized by an average value of n which may be a non-integer number.
In a preferred embodiment, the impregnation in step (iii) is achieved using a method
selected from the group consisting of resin transfer molding, vacuum assisted resin
transfer molding, liquid resin infusion, Seemann Composites Resin Infusion Molding
Process, vacuum assisted resin infusion, injection molding, compression molding, spray
molding, pultrusion, laminating, filament winding, Quickstep process or Roctool process.
More preferably, the impregnation in step (iii) is achieved using a liquid composite
molding process method selected from the group consisting of resin transfer molding,
liquid resin infusion, Seemann Composites Resin Infusion Molding Process, vacuum
assisted resin infusion, injection molding, and EADS vacuum assisted process (VAP®) .
— Pultrusion
For this method the state-of-the-art material are epoxy resins and polyesters. So far
cyanate esters have not been applied to this method. The pultrusion process can be
used to continuously manufacture bars and profiles with a regular cross-section or
hollow structure. The fiber reinforcement is continuous and the fibers are aligned
parallel to the production direction.
The reinforcement structures (made of glass or carbon or aramid fibers) are
impregnated from a resin bath with all components mixed. The resin formulation should
have a viscosity of less than 500 mPaxs and preferably no more than 300 mPaxs, at
the impregnation temperature.
Complete and uniform impregnation of the reinforcing fibers is of crucial importance in
the pultrusion process.
Subsequently, the composite material is fed into a heated die and drawn through it. As a
result the matrix starts to polymerize in order to produce a fiber reinforced bar with a
cross-section defined by the dimensions of the pultrusion die. Finally, the bar is cut to
the required length.
By using aromatic diamines (especially Lonzacure™ DETDA80) as catalysts in the
pultrusion process the mix viscosity can be further reduced, which helps to operate the
resin bath at a lower temperature. In order to achieve a certain and economically
production speed the concentration of the aromatic diamine needs to be higher. The
higher concentration guarantees that the pultruded bar is already polymerized and solid
on exiting the mold.
Gelation time and cure time can be designed very precisely and the curing time overall
can be reduced considering the reactivity data given in the working examples below.
— Filament Winding
For this method the state-of-the-art material are epoxy resins and polyesters. So far
cyanate esters have only been applied rarely and without catalysts to this method. For
the production of pressure vessels and convex geometries from composite materials,
filament winding is one of the most competitive technologies. The industrially available
impregnation method for the filament winding comprises the impregnation of the fibers
in an open bath. During the impregnation process the roving has to be spread out in
order to completely wet the single fiber filaments of the roving.
A filament winding apparatus then winds the tensioned and resin-impregnated fiber
bundle around a mandrel which defines the shape and dimensions of the final product.
The fiber bundles are applied under tension in order to achieve a high fiber/resin volume
ratio on the composite.
For filament winding the resin formulation should have a viscosity of less than about
500 mPaxs, preferably no more than about 300 mPaxs, at the impregnation
temperature. The reinforcement structures (made e. g . of glass, carbon, or aramid
fibers) are impregnated in a resin bath with all components mixed. Complete and
uniform impregnation of the reinforcing fibers is of crucial importance in the filament
winding process.
By using aromatic diamines (especially Lonzacure™ DETDA80) as catalysts the mix
viscosity can be further reduced, which helps to operate the resin bath at a lower
temperature. In order to achieve a certain and economically curing process a certain
concentration of the aromatic diamine is applied. The concentration guarantees that the
produced (e. g . cylindrical or elliptical) part can be cured at much lower temperature
than a pure cyanate ester resin (without catalyst) which results in lower internal stress
and higher part quality.
Gelation time and cure time can be designed very precisely and the curing time overall
can be reduced considering the reactivity data given in the working examples below.
The catalysts employed in the present invention are metal-free, and in particular free of
transition metals which may impair the properties (e. g . the electromagnetic properties)
of the final products or cause environmental or occupational problems. Preferably the
liquid mixture of the present invention is essentially free of soluble metal compounds.
"Essentially free" is to be understood to mean a metal content of no more than 10 ppm,
preferably no more than 5 ppm by weight.
In a preferred embodiment the catalyst (c) is selected from the group consisting of
aliphatic mono-, di- and polyamines, aromatic mono-, di- and polyamines, carbocyclic
mono-, di and polyamines, heterocyclic mono-, di- and polyamines, compounds
containing a five- or six-membered nitrogen-containing heterocyclic ring, hydroxyamines,
phosphines, phenols, and mixtures thereof.
Suitable catalysts include, without being limited thereto, phenols such as phenol,
p-nitrophenol, nonylphenol, pyrocatechol, dihydroxynaphthalene; tertiary aliphatic
amines such as trimethylamine, triethylamine, /,/V-dimethyl-octylamine and tributylamine
and their addition compounds such as /,/V-dimethyl-octylamine-boron
trichloride; cyclic tertiary amines such as diazabicyclo[2.2.2]octane, tertiary aromaticaliphatic
amines such as /,/V-dimethylbenzylamine, aromatic nitrogen heterocycles
such as imidazole, 1-methyl imidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole,
2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-undecylimidazole,
2-octadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, pyridine,
pyridines substituted with one or more Ci_4 alkyl and/or Ci_4 alkenyl groups, /V-methylpiperazine,
quinoline, isoquinoline and tetrahydroisoquinoline, quaternary and tertiary
ammonium salts such as tetraethylammonium chloride and triethylamine hydrochloride,
N-oxides such as pyhdine-/V-oxide, tertiary phosphines such as tributylphosphine and
triphenylphosphine, aminoalcohols such as 2-dimethylaminoethanol, 1-methyl-
2-dimethylaminoethanol, 1-(phenoxymethyl)-2-dimethylaminoethanol, 2-diethylaminoethanol,
1-butoxymethyl-2-dimethylaminoethanol, nitrogen heterocycles with
hydroxylated side chains such as 1-(2-hydroxy-3-phenoxypropyl)-2-methyl imidazole,
1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-
2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole,
1-(2-hydroxy-3-phenoxypropyl)-2-phenylimidazoline, 1-(2-hydroxy-3-butoxy propyl )-
2-methylimidazoline and /-(P-hydroxyethyl)morpholine, aminophenols such as
2-(dimethylaminomethyl)phenol and 2,4,6-tris(dimethylaminomethyl)phenol, diamines
such as 2-dimethylaminoethylamine, 2-diethylaminoethylamine, 3-dimethylaminon-
propylamine and 3-diethylamino-n-propylamine, and mercapto compounds such as
2-dimethylaminoethanethiol, 2-mercaptobenzimidazole and 2-mercaptobenzothiazole,
and other sulfur compounds such as methimazole ( 1-methyl-3H-imidazole-2-thione).
All these catalysts can react with the cyanate ester resin and/or the epoxy resin and are
thus covalently bound in the final product and not prone to leaching or diffusing out.
More preferably, the catalyst (c) is selected from the group consisting of aromatic
diamines of formula
38 42
(Ilia) (Nib)
wherein R3 1, R32 , R33, R36 , R36 , R37, R38 , R40 , R4 1 and R42 are independently selected
from hydrogen, Ci_ 4 alkyl, Ci_4 alkoxy, Ci_ 4 alkylthio and chlorine and R34 , R35 , R39 and
R43 are independently selected from hydrogen and C 1- 8 alkyl, and mixtures thereof and
Z 3 indicates a direct bond or a divalent moiety selected from the group consisting of
-O-, -S-, -S(=O)-, - S (=0) 2- -CH(CF 3)-, -C(CF 3)2- , - C (=0)-, -C(=CH 2)-,
-C(=CCl2)-, -Si(CH 3)2_ , linear Ci_i o alkanediyl, branched C4-1 0 alkanediyl, C3-8
cycloalkanediyl, 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, -N(R 44 ) - wherein R44 is
selected from the group consisting of hydrogen, linear Ci_i o alkyl, halogenated linear
C1-10 alkyl, branched C4-10 alkyl, halogenated branched C4-10 alkyl, C3-8 cycloalkyl,
phenyl and phenoxy.
In a preferred embodiment Z 3 is a methylene (-CH 2- ) group.
The expression C 4 alkyl" is herein meant to include methyl, ethyl, 1-propyl, 2-propyl
(isopropyl), 1-butyl, 2-butyl (sec-butyl), 2-methyl-1 -propyl (isobutyl) and 2-methyl-
2-propyl (terf-butyl) while the expression "Ci_ 8 alkyl" is meant to include the beforementioned
and all linear and branched alkyl groups having 5 to 8 carbon atoms
according to the definitions given above for linear Ci_io alkyl and branched C4_io alkyl.
In an especially preferred embodiment the catalyst (c) is selected from the group
consisting of 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6-diamine,
4,4'-methylenebis(2,6-diisopropylaniline), 4,4'-methylenebis(2-isopropyl-6-methylaniline),
4,4'-methylenebis(2,6-diethylaniline), 4,4'-methylenebis(3-chloro-2,6-diethylaniline),
4,4'-methylenebis(2-ethyl-6-methylaniline), 4,4'-methylenebis(/V-sec-butylaniline),
and mixtures thereof.
In another preferred embodiment the at least one di- or polyfunctional cyanate ester (a)
is a cyanate ester of formula (lc) wherein R 14 and R 15 are hydrogen and the average
value of n is from 1 to 20, more preferably from 1 to 15, even more preferably from 1 to
10, and most preferably from 1 to 5 .
In still another preferred embodiment the at least one di- or polyfunctional epoxy resin
(b) is selected from the group consisting of bisphenol A diglycidyl ether resins,
bisphenol F diglycidyl ether resins, A/,/V,0-thglycidyl-3-aminophenol, /, /,O-triglycidyl-
4-aminophenol, /V,/V,/V',/\/-tetraglycidyl-4,4'-methylenebisbenzenamine, 4,4',4"-methylidenetrisphenol
triglycidyl ether resins, naphthalenediol diglycidyl ethers, and mixtures
thereof.
In another preferred embodiment the liquid mixture obtained in step (i) comprises from
20 to 80 wt.% of the at least one di- or polyfunctional cyanate ester (a).
In another preferred embodiment the liquid mixture obtained in step (i) comprises from
20 to 79 wt.% of the at least one di- or polyfunctional epoxy resin (b).
In still another preferred embodiment the liquid mixture obtained in step (i) comprises
from 0.5 to 10 wt.% of the catalyst (c).
In another preferred embodiment the fiber structure provided in step (ii) is selected from
the group consisting of carbon fibers, glass fibers, quartz fibers, boron fibers, ceramic
fibers, aramid fibers, polyester fibers, polyethylene fibers, natural fibers, and mixtures
thereof.
In another preferred embodiment the fiber structure provided in step (ii) is selected from
the group consisting of strands, yarns, rovings, unidirectional fabrics, 0/90° fabrics,
woven fabrics, hybrid fabrics, multiaxial fabrics, chopped strand mats, tissues, braids,
and combinations thereof.
The liquid mixture obtained in step (i) may contain one or more additional components
selected from the group consisting of (internal) mold release agents, fillers, reactive
diluents, and mixtures or combinations thereof.
Internal mold release agents are preferably present in amounts of 0 to 5 wt.%, based on
the total amount of components (a), (b), and (c). Examples of suitable internal mold
release agents to be added to the liquid mixture obtained in step (i) are Axel
XP-l-PHPUL-1 (a proprietary synergistic blend of organic fatty acids, esters and amine
neutralizing agent) and Axel MoldWiz® INT-1850HT (a proprietary synergistic blend of
organic fatty acids, esters and alkanes and alkanols, supplier: Axel Plastics Research
Laboratories, Inc., Woodside NY, USA). Other mold release agents are usually rubbed
on a mold surface. Examples of those mold release agents are Frekote® 700-NC (a
mixture of hydrotreated heavy naphtha (60-1 00%), dibutyl ether ( 10-30%), naphtha
(petroleum) light alkylate (1-5%), octane (1-5%) and proprietary resin (1-5%); supplier:
Henkel AG & Co. KGaA, Dusseldorf, Germany) and Airtech Release All® 45 (which
contains 90-1 00% hydrotreated heavy naphtha (petroleum); supplier: Airtech Europe
SARL, Differdange, Luxembourg).
Fillers are preferably present in amounts of 0 to 40 wt.%, based on the total amount of
components (a), (b), and (c). They may be in particle, powder, sphere, chip and/or
strand form in sized from nano scale to millimeters. Suitable fillers may be organic, such
as thermoplastics and elastomers, or inorganic, such as glass, graphite, carbon fibers,
silica, mineral powders, and the like.
Reactive diluents are preferably present in amounts of 0 to 20 wt.%, based on the
amount of component (b). Examples of suitable reactive diluents are liquid mono-, di- or
trifunctional epoxy compounds derived from aliphatic or cycloaliphatic alcohols or
phenols, such as diglycidyl ethers of glycols, in particular 1,w -alkanediols having 4 to 12
carbon atoms, for example 1,4-(diglycidyloxy)butane or 1, 1 2-(diglycidyloxy)dodecane,
or the diglycidyl ether of neopentyl glycol, glycidyl ethers of linear or branched primary
alcohols having 8 to 16 carbon atoms, for example 2-ethylhexyl glycidyl ether or Ce-16
alkyl glycidyl ether, or the diglycidyl ether of 1,4-cyclohexanedimethanol.
In a preferred embodiment the liquid mixture obtained in step (i) contains little or no
additional (non-reactive) solvent such as acetone or butanone. Preferably it contains
less than 20 wt%, more preferably less than 15 wt.%, even more preferably less than
10 wt.% or 5 wt.%, each percentage being based on the total weight of components (a),
(b), and (c), or, most preferably, no solvent at all.
The curing step (v) may be performed using any heating technique, including co n
ventional techniques as well as innovative techniques such as Quickstep or Roctool
processes. The time required for curing the liquid mixture depends on its composition
and the curing temperature, it is typically in the range of about one hour to about 20
hours. A skilled person can easily determine suitable curing conditions based on the
guidance given by the working examples below.
The curing step (v) may further be followed by a post-curing heat treatment, preferably
at a temperature up to 300 °C for up to 10 hours.
The fiber-reinforced parts obtainable by the method of the invention exhibit a hightemperature
resistance, as given by the g value (determined by tan d measurement via
TMA) of preferably more than 100 °C, more preferably 120 to 160 °C, after demolding
and preferably more than 180 °C, more preferably 200 to 420 °C, after post-curing.
The fiber-reinforced parts obtainable by the method of the invention and its preferred
embodiments as described above are likewise an object of the invention.
The fiber-reinforced parts obtainable by the method of the invention may be used in
visible or non-visible application, including, but not limited to, fiber reinforced panels,
such as protective covers, door and flooring panels, doors, stiffeners, spoilers, diffusors,
boxes, etc., complex geometries, such as molded parts with ribs, parts with rotational
symmetry parts such as pipes, cylinders, and tanks, in particular fuel tanks, oil and gas
riser, exhaust pipes, etc., and massive or hollow profiles, such as stiffeners, spring
leaves, carriers, etc., and sandwich-structured parts with or without core structure, such
as blades, wings, etc., or carbon fiber-reinforced plastic molds for the manufacture of
high performance composite materials.
The following non-limiting examples will illustrate the method of the invention and the
preparation of the fiber-reinforced parts according to the invention. All percentages are
by weight, unless specified otherwise.
Examples:
Methods:
RTM resin transfer molding/resin injection
The process Resin Transfer Molding is described: The fiber reinforcement is placed in a
mold set; the mold is closed and clamped. The resin is injected into the mold cavity
under pressure. The motive force in RTM is pressure. Therefore, the pressure in the
mold cavity will be higher than atmospheric pressure. In contrast, vacuum infusion
methods use vacuum as the motive force, and the pressure in the mold cavity is lower
than atmospheric pressure.
The resin injection molding process is designed for high output (short cycle time) part
manufacturing under repetitive conditions, with very limited tolerances (concerning all
process parameters, e.g. such as viscosity, mix ratio, permeability of the reinforcement,
geltime, cycle time). It is most commonly used to process both thermoplastic and
thermosetting polymers.
Desired characteristic of the resin used in RTM:
Must have a low viscosity at a certain temperature as it is held in the
reservoir prior to injection
Must impregnate the fiber preform quickly and uniformly without voids
· Must gel as quickly as possible once impregnation occurs (fast cycle time)
Must possess sufficient hardness to be demolded without distortion
Low viscosity critical (<1 000 mPaxs at impregnation temperature to
impregnate preform loading of 50%)
Low viscosity requires less pressure to achieve adequate fiber wetting
· Injection temperature (typically elevated) of resin should be held as close as
possible to minimum viscosity to ensure preform impregnation, since higher
temperatures accelerate curing, thus cutting injection time.
The resin formulations developed (cyanate ester formulations and blends catalyzed with
amines) can be also applied in composite manufacturing processes with dynamically
changing mold temperatures, e.g. such as the Quickstep or Roctool processes.
Technical characteristic:
Cyanate ester or cyanate ester/epoxy blends resin systems could be cured with the
amines catalyst Lonzacure DETDA80 or other amines in RTM resin injection processes.
The cure time could be designed varying the catalyst amount (for example from 0.5 to
5 wt.% or more) which depend mostly by the injection temperature and mold
temperature applied for the process. Finally the cure cycle time could be reduced to
values in the order of 5-30 minutes, preferably 5-20 minutes. Post-cure treatment
between 180 °C and 300 °C, preferably between 180 °C and 220 °C, was applied in
order to achieve the desired high thermal and mechanical performance.
Example 1:
The formulation was a mix of cyanate ester Primaset™ PT-30 (formula lc,
R14 = R15 = H, n = 3-4) and bisphenol A epoxy resin (formula Mb, Q3 = Q4 = O,
R20 = R2 1 = R22 = R23 = R24 = R25 = R26 = R27 = H, Z2 = -C(CH 3)2- glycidyloxy moieties
in para position to Z2) . The liquid amine Lonzacure™ DETDA80 (formula Ilia, R3 1 = CH3,
R32 = R33 = C2H5, R34 = R35 = H, isomeric mixture of about 80% 3,5-diethyltoluene-
2,4-diamine and about 20% 3,5-diethyltoluene-2,6-diamine) was used as catalyst.
A mixture of 12.80 g (41 wt.%) of Primaset™ PT-30 and 18.1 0 g (59 wt.%) of bisphenol
A diglycidyl ether epoxy resin GY240 (Huntsman) was prepared. The viscosity of the
resin system is shown in Table 1 below:
Table 1: Viscosity of Primaset ™ PT-30 (41 wt.%)/Bisphenol A (59 wt.%)
The viscosity of the liquid catalyst amine Lonzacure™ DETDA80 is very low as shown
in Table 2 below.
Table 2 : Viscosity of Lonzacure™ DETDA80
The low viscosity and high fiber wetting potential of the resin system Primaset™ PT-30/-
bisphenol A epoxy + catalyst Lonzacure™ DETDA80 can provide good processability
parameters. The resin can be injected at temperatures between 50 and 80 °C with
viscosities below 1000 mPaxs.
The resin system must gel as quickly as possible once the impregnation is completed.
The gelation time can be controlled by varying the amount of catalyst and the tempera
ture as shown in Table 3 below. The amount of catalyst is given in percent by weight,
based on the amount of cyanate ester + epoxy resin.
Table 3 : Gel Time (Gelnorm) of Primaset™ PT-30/Bisphenol A Epoxy Resin +
Catalyst Lonzacure™ DETDA80
n. d.: not determined (too short)
By setting a mold temperature of, for example, 130-140 °C, the resin system containing
from 2 to 3 wt.% amine Lonzacure™ DETDA80 catalyst achieved sufficient hardness
within 5-20 min to allow demolding without distortion. Glass or carbon fiber composite
parts could be produced by this method. A summary of the technical parameters is
shown in Table 4 below.
Table 4 : Summary of Technical Parameters for RTM-Resin Injection:
After the cure cycle it was possible to demold the parts without distortion.
High temperature resistance (respectively a high g) can be achieved either through a
defined post-cure process step in an oven (temperature between 180 °C and 220 °C) or
during service in a high temperature environment.
The g glass transition temperature was measured by Thermal Mechanical Analysis
(TMA). The machine used was a Mettler Toledo instrument TMA SDTA840. The sample
dimensions were 6^6 mm2 (length c width) and 1.5 mm thickness. The test method
applied two heating ramps (first ramp: 25-220 °C @ 10 K/min and a second ramp 25-
350 °C @ 10 K/min). The g was evaluated on the second ramp. The results are shown
in Table 5 below.
Table 5 : Thermal Performance (Example 1)
Example 2 :
The formulation was a mix of cyanate ester Primaset™ PT-15 (formula lc,
R14 = R15 = H, n = 2-3) and bisphenol A diglycidyl ether epoxy resin. The liquid amine
Lonzacure™ DETDA80 was used as catalyst.
A mixture of 12.80 g (41 wt.%) of Primaset™ PT-15 and 18.1 0 g (59 wt.%) of bisphenol
A epoxy resin GY240 (Huntsman) was prepared. The viscosity of the resin system is
shown in Table 6 below:
Table 6 Viscosity of Primaset™ PT-15 / Bisphenol A Epoxy Resin
The low viscosity and high fiber wetting potential of the resin system Primaset™ PT-
15/bisphenol A epoxy resin + catalyst amine Lonzacure™ DETDA80 provide even
better processability parameters than the resin system described above in Example 1.
The resin can be injected at temperatures between 35 and 60 °C with viscosity lower
than 1000 mPaxs.
The resin system must gel as quickly as possible once the impregnation is completed.
The gelation time can be controlled by varying the amount of catalyst and the
temperature as can be shown in Table 7 below:
Table 7 : Gel Time (Gelnorm) of Primaset™ PT-15 (41 wt.%)/Bisphenol A Epoxy
(59 wt.%) resin + catalyst Lonzacure™ DETDA80
By, for example, setting the mold temperature to 120 °C, the resin system containing
from 3 to 5 wt.% amine Lonzacure™ DETDA80 catalyst achieves sufficient hardness to
allow demolding after about 10 min without distortion. Glass or carbon fiber composite
parts could be produced by this method. A summary of the technical parameters is
shown in Table 8 below.
Table 8 : Summary of the technical parameters RTM-resin injection:
After the cure cycle it was possible to demold the parts without distortion.
High temperature resistance (respectively a high g) can be achieved either through a
defined post-cure process step in an oven (temperature between 180 °C and 220 °C) or
during service in a high temperature environment.
The g glass transition temperature was measured by Thermal Mechanical Analysis
(TMA) as described in Example 1. The results are shown in Table 9 below:
Table 9 : Thermal Performance (Example 2)
— Vacuum assisted resin transfer molding (VARTM) and resin infusion
Former inventions were mostly addressing the prepreg technology or 1-component
resin formulations. Resin infusion requires resin systems with a viscosity (at infusion
temperature) of less than 500 mPaxs, preferably less than 300 mPaxs. The
reinforcement structures (made of glass or carbon or aramid fibers) are impregnated
from a resin pot with all components mixed. By using aromatic diamines (especially
Lonzacure™ DETDA80) the mix viscosity can be further reduced, which helps to
operate the resin pot at a lower temperature. Considering the size of the part, the
infusion time must be evaluated. Gelation time and cure time can be designed very
precisely and the curing time overall can be reduced considering the reactivity date in
Table 10 below.
Table 10: Gel Time (Gelnorm) of Primaset™ PT-30/Bisphenol A Epoxy Resin +
Catalyst Lonzacure™ DETDA80
n. d.: not determined (too short)
The viscosity of the blend Primaset™ PT-30 (68 wt.%)/Bisphenol A Epoxy (32 wt.%)
resin system is shown in Table 11 below:
Table 11: Viscosity of Primaset™ PT-30/Bisphenol A Epoxy
Example3
Vacuum assisted resin transfer molding (VARTM) and resin infusion:
TECHNICAL CHARACTERISTIC:
A flat glass mold was used. The mold was cleaned, and the surface was rubbed with a
mold release agent. In this test, the liquid release agent Release All® 45 from Airtech
was used.
The carbon fiber fabric was cut into 25x25 cm2 pieces and care was taken to prevent
fiber pullout during handling of the cut plies. 16 plies were cut for each of the
experimental laminates. In the test case, the carbon fabric fibers used were Toho Tenax
HTA40 E 3 (supplier: Toho Tenax Europe GmbH, Wuppertal, Germany). Then the
carbon fiber fabric layers prepared were laid on the mold surface. Care was taken to
build up a symmetric lay-up in order to prevent distortion during the post-cure stage.
In this example, an Airtech Omega Flow Line was used for both the resin feed and the
vacuum line. The dimension of the Omega Flow Line was the same as the width of the
carbon fiber layers on both sides (resin feed inlet and vacuum line outlet). Once the
resin was infiltrated on one side, the resin feed line was filled on its complete length
very quickly. After that, the resin infused across the whole carbon laminate lay-up
toward the vacuum outlet.
The following resin infusion auxiliary materials were utilized: An "all-in-one" peel ply and
release film layer (Fibertex Compoflex® SB1 50) was cut and placed directly in contact
over the carbon fiber layers. A resin distribution medium layer (Airtech Knitflow 105 HT)
was cut and installed on the top of the previous layup (carbon fibers and peel
ply/release film layers). The resin distribution medium allowed the spreading of the resin
quickly in the whole composite part. The distribution layer was positioned as well as a
basement of the Omega Flow Line (Airtech Omega Flow Lines OF750) for the resin
feed inlet. On the other side of the mold (vacuum line outlet), a resin distribution layer
and a Compoflex SB150 (Fibertex Nonwovens A/S, Aalborg, Denmark) layer were
placed as a basement for the Omega Flow Line. All layers of material in contact with the
mold were compressed to avoid "bridging" when vacuum was applied. High temperature
resin infusion connectors (Airtech VAC-RIC-HT or RIC-HT) were attached to the middle
of the resin feed inlet and vacuum outlet channels.
A customized rectangular vacuum bag was used which was heat seamed at three sides
of its perimeter and specially designed for the mold dimension (Airtech Wrightlon ®
WL5400 or WL7400). All the infusion assembly was set up inside the vacuum bag which
was finally heat seamed on the one open side of its perimeter. Two small holes were
punctured in the bag. The feed line and vacuum line connectors were attached to the
bag over the holes and nylon tubes were installed. The assembled mold was connected
with a resin source and a vacuum pump.
The whole mold assembly was installed inside an oven to infuse at the required
temperature. Full vacuum and temperature was applied to the bag assembly for 3 up to
12 hours before infusion was started. It was beneficial to apply to the fiber lay-up and
mold assembly the processing temperature conditions in order to improve the flow
process and to remove the moisture picked-up from the fiber layers.
The vacuum pump was turned-on with a vacuum of 3-5 hPa, and excellent sealing was
achieved by checking leakages. The oven temperature was increased to 80 °C at a
heating rate of 3-5 K/min.
350 g of the Primaset™ PT-30/Bisphenol A diglycidyl ether epoxy resin blend (a mix of
238 g cyanate ester Primaset™ PT-30 and 112 g bisphenol A epoxy resin (Huntsman
GY240)) was placed inside a vacuum oven at 80 °C and degassed at 3 hPa for 30 min
to remove any air bubbles present in the resin. Then the amine catalyst Lonzacure™
DETDA80 (3.1 5 g, 0.9 wt%) was added at 80 °C and mixed till complete
homogenization. The resin + amine catalyst system was placed in an oven at 80 °C and
degassed again at 5 hPa for 5-1 0 minutes to remove any air bubbles created during the
mixing with the catalyst.
The vacuum bag pressure was set to 10 mbar and the oven temperature was 80 °C.
Heating the resin to 80 °C reduced the viscosity to the range of 150-300 mPaxs. At this
viscosity, the Primaset™ PT-30/bisphenol A diglycidyl ether epoxy resin blend + amine
catalyst Lonzacure™ DETDA could be successfully infused within 20-30 minutes and
made to flow through the fibers under the bag.
The full vacuum of 10 hPa was kept till the resin reached cure point. The material was
cured under the bagging assembly using the following cure cycle:
80 °C-1 20 °C, 1 K/min; 2 h @ 120 °C; 120 °C-140 °C, 1 K/min; 2 h @ 140 °C
After curing the material could be easily demolded from the bagging assembly. A post
cure cycle can be applied as follows, in order to reach the mechanical and thermal
performances desired: 25 "C-220 °C, 0.5 K/min, 2 h @ 220 °C.
A summary of the technical parameters is shown in Table 12 below.
Table 12: Summary of the technical parameters of resin infusion:
The g glass transition temperature was measured by Thermal Mechanical Analysis
(TMA) as described in Example 1. The result is shown in Table 13 below:
Table 13: Thermal Properties (Example 3)
Post cure cycle 25-220 °C @ 0.5 K/min + 2 h @ 220 °C
q onset by TMA 280-290 °C
Example 4
Pultrusion:
TECHNICAL CHARACTERISTIC:
A rectangular metal pultrusion mold was used, that formed a composite profile of
20 10 mm2. The mold was cleaned, and the surface was rubbed with a mold release
agent (Chemlease® IC25).
The fiber reinforcement (carbon fiber Toho Tenax HTA (supplier: Toho Tenax Europe
GmbH, Wuppertal, Germany)) was formed by 16 rovings. The fibers were directly pulled
from the bobbin towards the resin bath.
The impregnated fibers entered the pultrusion mold and were pulled through the mold.
The mold comprised four differently controlled heating zones, starting with a
temperature of 150 °C and increasing to 160 °C, 170 °C and finally 180 °C at the mold
outlet.
A Primaset™ PT-30 / bisphenol A diglycidyl ether epoxy resin blend (350 g, mix of
238 g cyanate ester Primaset™ PT-30 and 112 g bisphenol A epoxy resin (Huntsman
GY240)) was mixed with 2% (7 g) of an internal mold release (Chemlease IC25,
supplier: Chemtrend). Then the amine catalyst Lonzacure™ DETDA80 (8.75 g,
2.5 wt.%) was added at 80 °C and mixed till complete homogenization. The resin +
amine catalyst system was placed into the resin bath which was kept at a constant
temperature of 65 °C. Then the pultrusion process started as decribed. Finally a post
cure cycle can be was applied: 25®220 °C @ 1 K/min + 2 h @ 220 °C.
The production speed achieved was 0.2 m/min. The samples manufactured showed a
g (by DMA) of 80 °C after molding and 300 °C after postcure.
A summary of the technical parameters is shown in Table 14 below.
Table 14: Summary of the technical parameters of pultrusion:
The T glass transition temperature was measured by Thermal Mechanical Analysis
(TMA) as described in Example 1. The result is shown in Table 17 below:
Table 15: Thermal Properties (Example 4)
Example 5
Filament winding:
TECHNICAL CHARACTERISTIC:
A cylindrical mandrel was used to form a composite pipe with an inner diameter of
40 mm. The mandrel was cleaned, and the surface was rubbed with a mold release
agent.
The fiber reinforcement (carbon fiber Toho Tenax HTA (supplier: Toho Tenax Europe
GmbH, Wuppertal, Germany)) was formed by 4 rovings. The fibers were directly pulled
from the bobbin through the resin bath which was kept at a constant temperature of
65 °C. The impregnated fibers were placed on the mandrel in different angles of ±30°
and 89° to form 18 layers, resulting in a pipe wall thickness of 4.4 mm.
The mandrel and the impregnated fibers placed hereon were kept at a constant
temperature of 80 °C.
A resin blend of Primaset™ PT-30 cyanate ester and bisphenol A diglycidyl ether epoxy
resin (350 g, a mix of 238 g Primaset™ PT-30 and 2 g bisphenol A epoxy resin
(Huntsman GY240)) was mixed with the amine catalyst Lonzacure™ DETDA80 (7 g,
2 wt%) at 70 °C complete homogenization. The resin + amine catalyst system was
placed into the resin bath at 65 °C. Then the filament winding process started as
described, followed by a precure cycle at 80 °C for 24 h, cooling to ambient temperature
(cooling rate 1 K/min), and demolding from the mandrel at ambient. Finally, the pipe
was subjected to a postcure treatment at 25 °C®220 °C, 1 K/min and 2 h @ 220 °C.
A summary of the technical parameters is shown in Table 16 below.
Table 16: Summary of the technical parameters by filament winding:
The g glass transition temperature was measured by Thermal Mechanical Analysis
(TMA) as described in Example 1. The result is shown in Table 17 below:
Table 17: Thermal Properties (Example 5)
Examples 6-14
Primaset ™ PT-30 cyanate resin was tested with various catalysts. The samples were
prepared by heating the resin to 95 °C, the adding the catalyst and mixing till complete
homogenization.
The samples were subjected to a curing cycle comprising heating from 25 °C to 140 °C
at 1 K/min and keeping at 140 °C for 30 min, followed by a post curing treatment
comprising heating from 25 °C to 200 °C at 1 K/min, keeping at 200 °C for 1 h, heating
from 200 °C to 260 °C at 1 K/min, and keeping at 260 °C for 1 h.
The g glass transition temperature was measured by Thermal Mechanical Analysis
(TMA) as described above. The test method applied two heating ramps (first ramp: 25-
250 °C @ 10 K/min, second ramp: 25-400 °C @ 10 K/min). The g was evaluated on
the second ramp. The results are compiled in Table 18, together with the methods
suitable for preparing fiber-reinforced parts from each composition.
Table 18
' Mixture of 3,5-bis(methylthio)toluene-2,4-diamine and 3,5-bis(methylthio)toluene-
2,6-diamine
2 4,4'-Methylenebis-(/V-sec-butylaniline)
3 /,/V-Dimethyl-n-octylamine, boron trichloride complex
4 Mixture of alkyl- and alkenylpyridines, comprising ca. 40% 5-(2-butenyl)-2-methylpyridines
(cis/trans mixture, ratio about 1:3), ca. 12% 2-allyl-5-ethylpyridine, ca.
9% 3,5-diethyl-2-methylpyridine, ca. 6% 5-ethyl-2-propylpyridine
Examples 15-28:
A blend of Primaset ™ PT-30 cyanate resin and bisphenol A diglycidyl ether epoxy resin
was tested with various catalysts. The samples were prepared by heating the resins to
95 °C, the adding the catalyst and mixing till complete homogenization.
The samples were subjected to a curing cycle comprising heating from 25 °C to 140 °C
at 1 K/min and keeping at 140 °C for 30 min, followed by a post curing treatment
comprising heating from 25 °C to 220 °C at 1 K/min and keeping at 220 °C for 2 h.
The g glass transition temperature was measured by Thermal Mechanical Analysis
(TMA) as described above. The test method applied two heating ramps (first ramp:
25®200 °C @ 10 K/min, second ramp: 25-350 °C @ 10 K/min). The g was evaluated
on the second ramp. The results are compiled in Table 19, together with the methods
suitable for preparing fiber-reinforced parts from each composition.
Table 19
Mixture of 3,5-bis(methylthio)toluene-2,4-diamine and 3,5-bis(methylthio)toluene-
2,6-diamine
4,4'-Methylenebis-(/V-sec-butylaniline)
/,/V-Dimethyl-n-octylamine, boron trichloride complex
Mixture of alkyl- and alkenylpyridines, comprising ca. 40% 5-(2-butenyl)-2-methylpyridines
(cis/trans mixture, ratio about 1:3), ca. 12% 2-allyl-5-ethylpyridine, ca.
9% 3,5-diethyl-2-methylpyridine, ca. 6% 5-ethyl-2-propylpyridine
Claims
1. A method for preparing a fiber-reinforced part based on cyanate ester or a cyanate
ester/epoxy blend, comprising the steps of
(i) providing a liquid mixture comprising
(a) from 15 to 99.9 wt.% of at least one di- or polyfunctional cyanate ester
selected from the group consisting of difunctional cyanate esters of
formula
wherein R1 through R4 are independently selected from the group
consisting of hydrogen, linear Ci_io alkyl, halogenated linear Ci_io alkyl,
branched C4_io alkyl, halogenated branched C4_io alkyl, C3-8 cycloalkyl,
halogenated C3-8 cycloalkyl, C1-1 0 alkoxy, halogen, phenyl and
phenoxy,
difunctional cyanate esters of formula
wherein R5 through R12 are independently selected from the group
consisting of hydrogen, linear Ci_io alkyl, halogenated linear Ci_io alkyl,
branched C4_io alkyl, halogenated branched C4_io alkyl, C3-8 cycloalkyl,
halogenated C3-8 cycloalkyl, C1-1 0 alkoxy, halogen, phenyl and
phenoxy;
and Z1 indicates a direct bond or a divalent moiety selected from the
group consisting of -0-, -S-, - S (=0)-, - S (=0) 2- -CH(CF 3)-,
-C(CF 3)2- , - C (=0)-, -C(=CH 2)-, -C(=CCI 2)-, -Si(CH 3)2- linear C IO
alkanediyl, branched C4-1 0 alkanediyl, C3-8 cycloalkanediyl, 1,2-
phenylene, 1,3-phenylene, 1,4-phenylene, -N(R 13) - wherein R 13 is
selected from the group consisting of hydrogen, linear Ci_io alkyl,
halogenated linear C1-1 0 alkyl, branched C4-10 alkyl, halogenated
branched C4-1 0 alkyl, C3-8 cycloalkyl, phenyl and phenoxy, and moieties
of formulas
wherein X is hydrogen or fluorine;
and polyfunctional cyanate esters of formula
(lc)
and oligomeric mixtures thereof, wherein n is an integer from 1 to 20
and R 14 and R 15 are independently selected from the group consisting
of hydrogen, linear C1-10 alkyl and branched C4-10 alkyl;
(b) from 0 to 84.9 wt.% of at least one di- or polyfunctional epoxy resin
selected from the group consisting of epoxy resins of formula
( Ma)
wherein Q1 and Q2 are independently oxygen or - N(G)- with
G = oxiranylmethyl, and R16 through R19 are independently selected
from the group consisting of hydrogen, linear Ci_io alkyl, halogenated
linear C1-10 alkyl, branched C4_io alkyl, halogenated branched C4_io
alkyl, C3-8 cycloalkyl, halogenated C3-8 cycloalkyl, C1-10 alkoxy,
halogen, phenyl and phenoxy;
epoxy resins of formula
(lib)
wherein Q3 and Q4 are independently oxygen or -N(G)- with
G = oxiranylmethyl, R20 through R27 are independently selected from
the group consisting of hydrogen, linear Ci_i o alkyl, halogenated linear
C1-10 alkyl, branched C4_io alkyl, halogenated branched C4_io alkyl, C3-8
cycloalkyl, halogenated C3-8 cycloalkyl, C1-10 alkoxy, halogen, phenyl
and phenoxy, and Z2 indicates a direct bond or a divalent moiety
selected from the group consisting of -O-, -S-, -S(=O)-, -S(=O)2-,
-CH(CF 3)-, -C(CF 3)2- -C(=O)-, -C(=CH 2)-, -C(=CCI 2)-, -Si(CH 3)2- ,
linear C1-10 alkanediyl, branched C4_io alkanediyl, C3-8 cycloalkanediyl,
1,2-phenylene, 1,3-phenylene, 1,4-phenylene, glycidyloxyphenylmethylene,
and -N(R 28)- wherein R28 is selected from the group
consisting of hydrogen, linear Ci_io alkyl, halogenated linear Ci_io alkyl,
branched C4_io alkyl, halogenated branched C4_io alkyl, C3-8 cycloalkyl,
phenyl and phenoxy;
epoxy resins of formula
(lie)
and oligomeric mixtures thereof, wherein m is an integer from 1 to 20,
Q5 is oxygen or -N(G)- with G = oxiranylmethyl, and R29 and R30 are
independently selected from the group consisting of hydrogen, linear
Ci_io alkyl and branched C4_io alkyl; and naphthalenediol diglycidyl
ethers;
and
(c) from 0.1 to 25 wt.% of a metal-free catalyst;
wherein the percentages of (a), (b) and (c) are based on the total amount of
(a), (b) and (c);
( ) providing a fiber structure
(iii) placing said fiber structure in a mold or on a substrate,
(iv) impregnating said fiber structure with said liquid mixture, optionally by
applying elevated pressure and/or evacuating the air from the mold and fiber
structure, at a temperature of 20 to 80 °C, and
(v) curing said liquid mixture by applying a temperature of 30 to 300 °C,
preferably 30 to 220 °C, for a time sufficient to cure said mixture.
The method of claim 1, wherein the impregnation in step (iii) is achieved using a
method selected from the group consisting of resin transfer molding, vacuum
assisted resin transfer molding, liquid resin infusion, Seemann Composites Resin
Infusion Molding Process, vacuum assisted resin infusion, injection molding,
compression molding, spray molding, pultrusion, laminating and filament winding.
The method of claim 1 or 2, wherein the catalyst (c) is selected from the group
consisting of aliphatic mono-, di- and polyamines, aromatic mono-, di- and
polyamines, araliphatic mono-, di- and polyamines, carbocyclic mono-, di and
polyamines, heterocyclic mono-, di- and polyamines, compounds containing a fiveor
six-membered nitrogen-containing heterocyclic ring, hydroxyamines,
phosphines, phenols, and mixtures thereof.
The method of claim 3, wherein the catalyst (c) is selected from the group con
sisting of /,/V-dimethyl-octylamine-boron trichloride complex, 2-ethyl-4-methylimidazole,
2-ethylimidazole, /,/V-dimethyl-benzylamine, 2,4,6-tris(dimethylaminomethyl)
phenol, 5-ethyl-2-methylpyridine, niacinamide, 1-butyl-3-methylpyridinium
dicyanamide, and mixtures thereof.
The method of claim 3, wherein the catalyst (c) is selected from the group
consisting of aromatic diamines of formula
(Ilia) (Nib)
wherein R3 1, R32, R33, R36, R36, R37, R38, R40, R4 1 and R42 are independently
selected from hydrogen, Ci_4 alkyl, Ci_4 alkoxy, Ci_4 alkylthio, and chlorine; R34 ,
R35, R39 and R43 are independently selected from hydrogen and C1- 8 alkyl, and
mixtures thereof; and Z3 indicates a direct bond or a divalent moiety selected from
the group consisting of -O-, -S-, -S(=0)-, -S(=0) 2- , -CH(CF 3)-, -C(CF 3)2- ,
-C(=O)-, -C(=CH 2)-, -C(=CCI 2)-, -Si(CH 3) - , linear Ci_i 0 alkanediyl, branched
C 4-10 alkanediyl, C3-8 cycloalkanediyl, 1,2-phenylene, 1,3-phenylene,
1,4-phenylene, and -N(R 44)- wherein R44 is selected from the group consisting of
hydrogen, linear C1-10 alkyl, halogenated linear C1-10 alkyl, branched C 4-10 alkyl,
halogenated branched C 4-10 alkyl, C3-8 cycloalkyl, phenyl and phenoxy.
The method of claim 5, wherein the catalyst (c) is selected from the group
consisting of 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6-diamine,
3,5-bis(methylthio)toluene-2,4-diannine, 3,5-bis(methylthio)toluene-2,6-diannine,
4,4'-methylenebis(2,6-diisopropylaniline), 4,4'-methylenebis(2-isopropyl-6-methylaniline),
4,4'-methylenebis(2,6-diethylaniline), 4,4'-methylenebis(3-chloro-2,6-diethylaniline),
4,4'-methylenebis(2-ethyl-6-nnethylaniline), 4,4'-methylenebis(/V-secbutylaniline),
and mixtures thereof.
7 . The method of any of claims 1 to 6, wherein the at least one di- or polyfunctional
cyanate ester (a) is a cyanate ester of formula (lc) wherein R14 and R15 are
hydrogen and the average value of n is from 1 to 20, preferably 1 to 5 .
8 . The method of any of claims 1 to 7, wherein the at least one di- or polyfunctional
epoxy resin (b) is selected from the group consisting of bisphenol A diglycidyl
ether resins, bisphenol F diglycidyl ether resins, A/,/V,0-thglycidyl-3-aminophenol,
A/,/V,0-thglycidyl-4-aminophenol, /V,/V,/V',/V'-tetraglycidyl-4,4'-methylenebisbenzenamine,
4,4',4"-methylidenetrisphenol triglycidyl ether resins, naphthalenediol
diglycidyl ethers, and mixtures thereof.
9 . The method of any of claims 1 to 8, wherein the liquid mixture obtained in step (i)
comprises from 20 to 80 wt.% of the at least one di- or polyfunctional cyanate
ester (a).
10 . The method of any of claims 1 to 9, wherein the liquid mixture obtained in step (i)
comprises from 20 to 79 wt.% of the at least one di- or polyfunctional epoxy resin
(b).
11. The method of any of claims 1 to 10, wherein the liquid mixture obtained in step (i)
comprises from 0.1 to 10 wt.% of the catalyst (c).
12 . The method of any of claims 1 to 11, wherein the liquid mixture obtained in step (i)
comprises less than 20 wt.%, based on the total weight of the liquid mixture, of a
solvent.
13 . The method of claim 12, wherein the liquid mixture obtained in step (i) comprises
less than 10 wt.%, based on the total weight of the liquid mixture, of a solvent.
14. The method of claim 13, wherein the liquid mixture obtained in step (i) is solventfree.
15 . The method of any of claims 1 to 14, wherein the fiber structure provided in step
(ii) is selected from the group consisting of carbon fibers, glass fibers, quartz
fibers, boron fibers, ceramic fibers, aramid fibers, polyester fibers, polyethylene
fibers, natural fibers, and mixtures thereof.
16 . The method of any of claims 1 to 15, wherein the fiber structure provided in step
(ii) is selected from the group consisting of strands, yarns, rovings, unidirectional
fabrics, 0/90° fabrics, woven fabrics, hybrid fabrics, multiaxial fabrics, chopped
strand mats, tissues, braids, and combinations thereof.
17 . The method of any of claims 1 to 16, wherein the liquid mixture obtained in step (i)
comprises one or more additional components selected from the group consisting
of mold release agents, fillers, reactive diluents, and combinations thereof.
18 . A fiber-reinforced part obtainable by the method of any of claims 1 to 17 .
19 . The fiber-reinforced part of claim 18, being selected from the group consisting of
fiber reinforced panels, complex geometries, parts with rotational symmetry parts,
massive and hollow profiles, and sandwich-structured parts.