Note: Descriptions are shown in the official language in which they were submitted.
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K- 1 8~33/A/CGW 26
Curable epoxv resin composition
The present invention relates to a curable epoxy resin compositi~n comprising ~m epoxy
resin consisting of a mixture of a tetraglycidyl compound of a binuclear subsfituted
diamine and an aromatie glycidyl ether containing at least two glycidyl ether groups in the
molecule, a diaminodiphenylsulfone as hardener and, in addition, a thermopastic resin
having a glass transition temperature of least 150C, and to the use of said composition,
especially as matrix resin for making prepregs.
It is known that the properties of curable epoxy resin compositions can be modified by the
addition of specific thermoplastic resins. For example, it is disclosed in EP-~-0 108 476
that the addition of the polyetherimide ULTEM(~) to curable epoxy resin compositions
such as N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane and diaminodiphen-
ylsulfone is able to increase the viscosity of said mixtures and to enhance the flexibility of
the moulded articles obtained.
It has now been found that, by modifying an epoxy resin composition containing two
specific epoxy resins with certain thermoplastic resins, it is possible to improve the
processing properties of the curable rnixture, such as goocl flow properties ov~r longer
processing times. Tn addition, the rnoulcled articles prepared from the eurable mixture s)f
the invention have improved flexural stren~th and, in particular, markedly enhanced
flexibility, The surprisingly good compatibility of the curable epoxy resin composition
with thermoplastic resins such as ULTEM~ also makes it possible to add larger amounts
of thermoplastic without any demixing.
Thus the present invention relates to a curable epoxy resin composition comprising
(a) 30 to 70 parts by weight of a tetraglycidyl compound of -formula I
-2- ~ Z
~ CH2~ CH- CH2~ N ~ CH2~ N t CH2- CH- CH2) (I)
wherein Rl, R2, R3 and R4 are each independently ~ one another a hydrogen atom, a
halogen atom or Cl-C4alkyl, with the proviso that at least one of the substituents Rl to R~
is Cl-C~alkyl,
(b) 70 to 30 parts by weight of an aromatic glycidyl ether containing on average 2.0 to
3.0 glycidyl ether groups in the molecule, SUC}I that the amount of (a) and (b) together is
100 parts by weight,
(c) a diaminodiphenylsulfone in an amount such as to supply 0.6 to 1.3 equivalents of
amino hydrogen atoms per I epoxide equivalent of the epoxy resin component consisting
of (a) and (b), and
(d) I to 50 parts by weight, based on 100 parts by weight of (a) and (b), of a thermoplastic
resin dissolved therein having a glass transition temperature of at least 150C.
The composition of this invention preferably contains (a) 40 to 60 parts by weight of a
tetraglycidyl compound of formula I and (b) 60 to 40 parts by weight of an aromatic
glycidyl ether.
The compounds of formula I are known and are disclosed, for example, inEP-~-0 143 075 ancl in JP Kokai 84-078.
Preferrecl haiogen substitllc nts are bromo or chloro.
Preferred compounds of formula I are those wherein at least one of the substituents R1 to
R~ is methyl, ethyl or isopropyl. Most preferably the compositions of this invention
contain a compound of forrnula 1, wherein Rl and R3 are each hydrogen and R2 and R4 are
each ethyl.
Suitable aromatic glycidyl ethers (b) are typically those epoxy compounds which are
obtained by reacting compounds containing two or three phenolic hydroxyl groups per
molecule with suitable epihalohydrins such as epichlorohydrin, under alkaline conditions
or else in the presence of an acid catalyst, followed by tTeatment with alkali. They may be
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derived from mon~nllclear phenols, swch as resorcinol and hydroqllinone, or frompolynuclear phenols, such as bis(4-hydroxyphenyl)methane, 4,4'-dihydroxydiphenyl, 1,5-,
1,~-, 2,3- or 2,7-dihydroxynaphthalene, bis(4-hydroxyphenyl)sulfone, 1,1,2,2-tetrakis-
(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyyhenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane and novolaks which are in turn derived from aldehydes, such as
formaldehyde, acetaldehyde, chloral and furfurylaldehyde, and phenols, such as
unsubstituted phenol and phenols, which are substituted at the ring by chlorine atoms or
alkyl groups containing up to 9 carbon atoms, typically 4-chlorophenol, 2-methylphenol
and 4-tert-butylphenol.
The cited epoxy compounds are known and some are commercially available.
The compositions of the invention preferably contain aromatic glycidyl ethers containing
on average 2.0 to 2.2 glycidyl ether groups in the molecule. More particularly, the
aromatic glycidyl ether (b) of the novel composition is bisphenol A or bisphenyl F
diglycidyl ether, the diglycidyl ether of a dihydroxynaphthalene or a mixture of said
glycidyl ethers.
The composition of this invention preferably contains the diaminodiphenylsulfone (c) used
as hardener in an amount sufficient to provide 0.8 to 1.0 equivalent of amino hydrogen per
I epoxy equivalent.
Viaminodiphenylsulfones are likewise known and some are commercially av~ailable. The
composition of the invention preferably contains 4,4'-diaminodiphenyls~llfone as hardener
(c).
Tllermnplastic resins (d) which may be used in the curable compositions of this invention
~are all thosc known polymers which have a sumciently high glass transition temperature
(Tg), i.e. Tg > 150C, and which are miscible with the epoxy resin hardener system in
question. On account of their properties, particularly suitable thermoplastic resins are
polysulfones or polyethersulfones which contain amino groups in the chain, polyimides or
polyetherimides and, pre~erably, polyimides and polyetherimides. Thermoplastic resins
having a glass transition temperature in the range from 180 to 350C, preferably from 190
to 250C, are especially preferred. If polyetherimides are used as thermoplastic resins,
polymers having a Tg in the range from 220 to 250C are especially preferred. Ifpolyimides are used, polymers having a Tg in the range f3 om 280 to 340C are preferred.
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Polyamide-imides are also suitable.
Mixtures of two or more thermoplastic resins can also be used as component (d).
Particularly suitable thermoplastic resins (d) are polyimides such as
- the polyimides containing phenylindane units disclosed in US patent 3 856 752 and in
EP-A 92 524, especially those having a glass transition temperature of about 305C and
an average molecular weight of 65 000, for exan~ple Ma~imid(~ 5218 sold by
Ciba-Geigy,
- the homo- and copolyimides of at least one aromatic tetracarboxylic acid and at least
one aromatic diamine disclosed for example in US patent 4 629 777, and
- thehomo-andcopolyimidesdisclosedinEP-A 162017,EP-A 181 837andin
US patent 4 629 685.
Preferred thermoplastic resins (d) are also the polyetherimides sold by General Electric
under the registered trademark Ultem(~ (e.g. as Ultem(3) 1000). Further preferred
therrnoplastic resins are polyethersulfones, such as Victrex PES l(X) P sold by ICI or Udel
P 1800 sold by Union Carbide.
Suitable polyamide-imides are typically the compounds disclosed in US patents
3 894 114, 3 948 835; 3 926 911 and 3 950 408.
If the thermoplastic resin td) is a polysulfone or polyethersulfone containing amino groups
in the chain, then it is suitably one having an inherent viscosity (rijnh) of 0.02 to 1.0,
measured in a I % solution of the polymer in N-methylpyrrolidone at 25C anc'i which
contains, based on the total number of structural units present in the polymer, 1(}() to
5 mol % of structural repeating unit of formula Il or III
C --Ar--O ~ (Il) or
~ ~ ~ ~3} (III)
~s~
-5
and 95 to O mol % of a structural repeating unit of formula IV
--~ X ~3 0 - Ar- O ~ (IV)
wherein
X is -SO2- or-CO-, and
Ar is a group of -formulae IVa to IVe
IVa), wherein a is O or 1,
~3 (IVb), X~ ~IVc),
(IVd), wherein b is 1 or 2, or
~3 Z ~ Z--~3 (IVe)
wherein Z is -CO-, -SO2-, -SO-, -S-~ O-, -C(CH3)2, -C(CF3~2, -C~l2- or - lc-
C6Hs
which group is unsubstituted or substituted by one or more Cl-C4alkyl or C1-C4alkoxy
groups or halogen atoms.
T hese polyarylene ethers may be prepared typically by reacting
1,3-dichloro-4-nitrobenzene or a mixture of 1,3-dichloro-4-niirobenzene and a dihalo
compound which is present therein in an amount of g5 mol %, preferably 90 mol %, of
formula V
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Hal ~ X ~3 Hal (V),
wherein Hal is a halogen atom, preferably a chlorine or fluorine atom, and X is as defined
above, with a diphenol of formula VI
HO-Ar-OH (VI),
wherein Ar is as defined above, or by polycondensing 2,4-bis(4-hydroxyphenoxy)aniline
or a mixture of 2,4-bis(4-hydroxyphenoxy)aniline and a diphenol of formu]a Vl contained
therein in an amount of 95 mol %, preferably 90 mol %, with a halogen compound of
forrnula V, in the presence of alkali and in an aprotic solvent, until the polyarylene ether
so nbtained has a lli.,h of 0.02 to 1.0, and subsequently converting the nitro group
containing polyarylene ether in known manner into an amino group containing
polyarylene ether by complete catalytic reduction of the nitro groups.
The alkali used in this process is normally an allcali metal carbonate or alkaline earth
metal carbonate, such as sodium, potasssium or calcium carbonate. However, it is also
possible to use other alkaline reagents such as sodium hydroxide, potassium hydroxide or
calcium hydroxide.
Polar aprotic solvents which may be used in the process for the prepnration of the
poly~rylene ether resins are typically diethyl acetamide, tetramethylurea,
N-methylcaprolactam and, preferably, dimethyl acetamide or N-methylpyTroliclone.
The reaction is conveniently carried out at elevated temperature, preferably in the range up
to the reflux temperature of the solvent, i.e. up to about 250C.
The composition of this invention preferably contains a therrnoplastic resin (d~ in an
amount of 15 to 30 parts by weight, based on 100 parts by weight of (a) and (b).
The composi~ion of the invention preferably also contains a polyimide or polyetherimide
as thermoplastic resin.
The compositions of the invention can be prepared by thoroughly mixing all components
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or dissolving them in one another, and the indiviclual components can be added in any
o}der. The thermoplastic resin may be dissolved in the epoxy resin by heating and, after
cooling, the other ingredients can be added. It is, however, also possible to prepare a
solution of the thermoplastic resin in an inert solvent, typically methylene chloride, and to
mix said solution with the epoxy resin-hardener mixture.
The compositions of the invention have many uses and are suitable for example as casting
resins, laminating or impregnating resins, moulding materials, sealing compounds and
insulating compounds in the electrical engineering field and, preferably, as adhesives and
matrix resins for composites, especially for making prepregs for the preparation of
fibre-reinforced plastics.
~f desired, especially when concurrently using modifiers, the compositions of this
invention can be dissolved in an organic solvent such as ~oluene, xylene, methyl ethyl
ketone, methylene chloride, or a solvent or mixture of solvents commonly ernployed in the
coating industry. Such solutions are particularly suitable as impregnating or coating
compositions~
The curable compositions of this invention can also be blended, prior to the cure, in any
phase with conventional modifiers, such as extenders, fillers and reinforcing agents,
pigments, dyes, organic solvents, plasticisers, levelling agents, thixotropic agents, flame
retardants or mould release agents. Typical examples of extenders, reinforcing agents,
fillers and pigments which can be used in the curable compositions of this invention are:
liquid cumene-indene resins, textile fibres, glass fibres, asbestos fibres, boron fibres,
carbon fibres, polyethylene powder, polypropylene powder, quartz powcler, mineral
silicates such as mica, lasbestos powder, ground shale, kaolin, powdered chalk, antimony
trioxide. bentones, lithopones, barite, titanium dioxide, carbon black, oxide pigments such
as iron oxide, or metal powders such as aluminium powder or iron powder. If the
compositions of the invention are used for making prepregs, it is especially desirable to
add ground fibres.
Levelling agents which may be added to the curable compositions, especially for surface
protection, are typically silicones, liquid acrylic resins, cellulose acetobutyrate,
polyvinylbutyral, waxes, stearates and the like (some of which may also be used as mould
release agents).
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Sllitable plasticisers for modifying the curable compositions are typically diblltyl, dioctyl
and dinonyl phthalate, tricresyl phosphate, trixylenyl phosphate and
diphenoxyethylformal.
The compositions of the invention are preferably cured by heating them to a temperature
in the range from 120 to 250C, preferably from 160 to 220C. The cure can also be
effected in known manner in two or more steps, the first curing step being carried out at
low temperature and the postcure at higher temperature.
If desired, active diluents may be added to the curable compositions to lower the viscosity,
Exemplary of such active diluents are neopentyl glycol ether, butanediol ether or
hexanediol diglycidyl ether.
The invention further relates to the use of the novel compositions for the preparation of
cured articles, as well as for making prepregs for the preparation of fibre-reinforced
composites. The prepregs can be made in a manner known per se, typically by the
impregnating method in the presence of one of the solvents referred to above, of a
halogenated solvent, typically methylene chloride, or in the hot melt process.
The moulded articles obtained in this invention are distinguished in general by high glass
transition temperatures while simultaneously having high mechanical strength and, in
particular, by excellent flexural strength and very high flexibility.
Only in the following Examples is the amount given in grams instead of parts by wcight.
The following compouncls are used in the Examples as epoxy resins or therrnoplastic
resins.
Epoxv resin A: N,N,N',N'-tetraglycidyl derivative of 4,~'-dian~ino-3,3'-diethyldiphenyl-
methane with an epoxy value of 7.95 equivalents~g and a viscosity of 9500 mPa s at
25C.
Epoxy resin B: bisphenol A diglycidyl ether with an epoxy value of 7.95 equivalents/kg
and a viscosity of lo4-1.2-104 mPa-s at 25C.
Epoxy resin C: bisphenol F diglycidyl ether with an epoxy value of 5.5 to
2~S56~2
5.9 equivalents/kg and a viscosity of 3000~10 000 mPa s at 25C,
Epoxy resin D: phenol-novolak epoxy resin with an epoxy value of 5.6 to5.8 equivalents/kg and a melt viscosity of 1 }00-1700 mPa s at 50C.
Polyetherimide 1: Polyetherimide Ultem~ 1000 (General Electric) with a glass transition
temperature (Tg) of 219C and containing the sutructural repeating unit of formula
O O
r 11 11
~ N ~ ~ e3 ~C N ~3
Polvimide II In a 4.5 Iitre sulfonating flask equipped with stirrer, thermometer, water
separator, condenser and gas inlet pipe, 261.72 g (1.2 mol) of pyromellitic dianhydride are
added at 5C over 1 hour in 4 portions to a solution of 247.1 g (0.875 mol) of
3,3'-diethyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane and 66.86 g (0.375 mol) of
2,4-diethyl-6-methyl-1,3-phenylenediamine in 1.5 Iitres of N-methylpyrrolidone (NMP).
After 2 hours, the ice bath is removed and the reaction solution is stirred overnight at room
temperature under nitrogen. To the reaction solution are added 750 ml of xylene and water
is removed as an azeotrope under reflux in the water separator. The xylene is then
removed from the reaction solution by distillation and the still warm solution is poured,
with efficient stirring, into 15 litres of water. The precip;tate is isolated by filtration,
mixed a second time with 5 litres of water, isolated by filtration, and dr;ed un~ler vacuum
at 1()0C. Yielcl: 526 g (98 % of theory) of a yellow granulate which dissolves in
me,thylene chloricle to form a clear solution and has a number average molecular weight
(Mn) of 13 300 and a weight average molecular weight (Mw) of 35 380, detelmined by gel
permeation chromatography in tetrahydrofuran. The amine value (titration in
phenol/chloroforrn with 0.1 N HCIC)~) is 1.19 meq./g. The Tg, measured by differential
scanning calorimetry (DSC), is 352C.
Example 1:
a) 30 g of polyetherimide I are dissolved in 50 ml of methylene chloride. To the solution
are added 50 g (0.40 equivalent) of epoxy resin A and 50 g (0.30 eq.) of epoxy resin C.
With stirring, the methylene chloride is removed by evaporation at 50C. The mixture is
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heated to 140C and 40 g (0.65 eq.) of 4,4'-diaminodiphenylsulfone (DDS) are addell.
After 10 minutes (min.) the DDS has dissolved. The mixture is evacuated to remove the
air bubbles, poured into preheated Anticorodal moulds measuring 80x8ax4 mm and cured
for 4 hours (h) at 180C.
The mixture is slightly tacky at room temperature. The cured product has the following
properties:
glass transition temperature Tgo (TMA) = 197C
glass transition temperature Tg ~TMA) = 207C
flexural strength (SF) (ISO 178) = 168 MPa
flexural elongation (FE) (ISO 178) = 9.0 %-
Tgo= onset of glass transition
Tg = temperature of maximum penetration speed
TMA = thermomechanical analysis; heating up rate = 10C/min~
b) Using 20 g of polyetherimide I and otherwise repeating the procedure of Example 1 a),
cured products with the following properties are obtained:
Tgo (TMA) = 182C
Tg (TMA) = 189C
FS = 169 MPa
FE =7.0%
c) Using 25 ~g of polyetherimide I and 50 g (().27 eq.) of epoxy resin B in place of 50 g of
epoxy resin C und otllerwise repeating the procedure of Example la), cured products with
the following properties are obtained:
Tgo (TMA) = 192C
Tg (TMA) = 200C
FS = 162 MPa
FE =7.8 %.
Example 2: Preparation of a carbon fibre laminate
In accordance with the general procedure of Example la), a resin mixture of 100 g of
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epoxy resin A, 100 g of epoxy resin D, 84 g of DDS and 50 g of polyetherimide I is
prepared. The resin composition is applied with a doctor knife to a xilicone-treated paper
on a preheated drum (drum take-up). A carbon fibre ("T-300 6K" sold by Toray) is wound
onto the resin, while the resin film is heated locally to c. 120C by IR heating. A 2 mm
thick unidirectional laminate is prepared from the prepreg by curing for 4 h al 1 80~C in an
autoclave ~pressure S bar).
The laminate has the following properties:
Tgo (TMA~ = 200C
Tg (TMA) = 217C
FS (9Q in fibre direction) = 112 MPa
interlaminary shear strength (ISS) (DIN 2g971)
at 20C = 100 MPa
at 1 20C = 69 MPa
at 1 60C = 54 MPa.
After storage for 14 days in water at 71C the following properties are determined:
water absorption = 0.8 %
ISS at 20C = 95 MPa
ISS at ] 20C = 54 MPa.
Example 3: Using 30 g of polyimide II, 50 g of epoxy resin A, 50 g of epoxy resin C and
35 g of DDS, and otherwise carrying out the procedure of Example 1, the following
properties of the cllred product are determined:
Tgo (TMA) = 1 82C
Tg (TMA) = 1 96C
FS - 156 MPa
FE = 7.8%.
Example 4: Using 35 g of a polysulfone obtained from 38.5 mol of the structural repeating
unit of formula II, wherein Ar is the radical ~3 C(CH3)2~;~, and from
2.5 mol of the structural repeating unit of formula IV, wherein Ar has the givcn meaning
and X is -SO2-, and having a Mn= 8 500 and Mw= 28 500 and an amine value of 0.13meq./g, sn g of epoxy resin A, 50 g of epoxy resin B as well as 40 g of DDS, and
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repeating the procedure described in Example 1, the following properties of the cured
procluct are determined:
Tgo (TMA) = 198C
Tg (TMA) = 207C
FS = 149 MPa
FE = 9.1%.
