Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
K-17325/=
A process ~r the pr~para~ioll of epoxy ~ompounds
The present invention relates to an improved process for the preparation of epoxy com-
pounds, and to the manufacture of cured products from these compounds.
Epoxy resins have for a long time been employed, inter alia, in the electronics industry.
In recent years there has been a steady increase in the purity requirements for such resins.
In par~icular, small amounts of ionic or hydrolysable halogen may have a detrimental
ef-fect. Also, there is an increasing demand for resins with as high as poss;ble a degree of
epoxidation. Epoxy resins are generally prepared by reacting compounds having reactive
hydrogen atoms, preferably phenols, with epichlorohydrin. For the preparation of resins
with a low halogen content there are also known processes in which compounds having
ethylenically unsaturated bonds are epoxidised. Normally, in the case of allyl com-
pounds, such compounds are aromatic C-allyl compounds, which are epoxidised withperacids, for example peracetic acid. Examples of such reactions can be found inEP-A-205,402.
The epoxidation of ethylenically unsaturated compounds with dimethyldioxirane offormula I is known per se.
CH3
CHX¦
For example, in J. Org. Chem., 51, 1925-6 (1986) P.F.Corey et aL describe the reaction of
-unsaturated carboxylic acids, inter alia cinnamic acid, with dimethyldioxirane. Also,
in 3. Org. Chem., 47, 2670-3 (1982) G. Cicala et ah describe the reaction of aliphatic allyl
alcohols with dimethyldioxirane as epoxidising reagent.
The epoxidation of aromatic allyl ethers with peracids is described, for example, in
2~
U~-A-3,957,873. This reaction has proved as a rule to give only moderate yields and
epoxy contents. Furthermore, the use of peracids in large scale industrial processes
represents a safety risk.
It has now surprisingly been found that high yields and high epoxy contents can be ob-
tained in the epoxidation of aromatic allyl ethers if the reaction is c~ried out with di-
oxiranes. Furtherrnore, the safety risk in such epoxidations can be reduced in comparison
with epoxidation using peracids.
The present invention relates to a process for the preparation of epoxy compounds from
aromatic allyl ethers having at least one radical of formula II
Rl
O ~ R2 (II),
R3
bonded directly to the aromatic nucleus, in which each of Rl, R2 and R3, independently of
the others, is hydrogen or Cl- C6alkyl, especially methyl and, more especially, hydrogen,
which comprises epoxidising the starting material, as such or dissolved in an inert solvent,
with a dioxirane, approximately from 1 to 20 mols of clioxirane being used per allyl
group.
Preferred aromatic allyl ethers for use in the process of the invention include compounds
of formula III or compounds that consist essentially of recurring structural units of
formula IV or V
Rl R2
I Rl ~E~3
A- L ~3 R2 ~ 6 }n
2~7
- 3 -
--~--CH~ CH2~_
R3 Rl (V),
~/~=<
in which m is 1, 2, 3 or 4, n is an integer of from 2 to 12; p is an integer of from 2 to 100,
q is 0, 1, 2 or 3, R1, R;~ and R3 are as defined above, R4 is Cl-C5alkyl or halogen, Rs and
R6 are each independently hydrogen or Cl-C6alkyl and A is a m-valent aromatic radical of
a phenol after removal of the hydroxy groups.
Any radicals representing Cl-C6alkyl are branched or preferably straight-chain alkyl
radicals. Examples are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-bu~yl, tert.-butyl,
n-pentyl or n-hexyl.
Ethyl, n-propyl or n-butyl, but especially methyl, is preterred.
Tlle index m is preferably 2. The index n is preferably from 3 to 6 and the index p is pre-
ferably from 5 to 40. The index q is preferably 1 and more especially 0. R4 as halogen is
usually chlorine or bromine.
Examples of preferred compounds from which the allyl ethers used in the process of the
invention are derived are mono- or poly-nuclear monophenols, such as phenol, cresols or
chlorophenol, or especially mono- or poly-nuclear polyphenols, such as resorcinol, hydro-
quinone, bis-(hydroxyphenyl)-methane (bisphenol F), 2,2-bis-(4-hydroxyphenyl)-prop.me
(bisphenol A), brominated 2,2-bis-(4-hydroxyphenyl)-propane, bis-(4-hydroxyphenyl)-
ether, bis-(4-hydroxyphenyl)-sulfone, 1,3,5-trihydroxybenzene, 1,1,2,2-tetrakis-~4-
hydroxyphenyl)-ethane, novolaks, which can be obtained by condensing aldehydes, such
as formaldehyde, acetaldehyde, chloral or furfuraldehyde, with unsubstituted or alkyl- or
halogen-substituted phenols, such as phenol, the above-described bisphenols, 2- or
4-methylphenol, 4-tert.-butylphenol, p-nonylphenol or 4-chlorophenol, or polyvinyl-
phenols, such as poly-p-vinylphenol.
The allyl ether starting materials can be prepared in a manner known ~ se from these
mono- or poly-phenols by etherification with an allyl halide, especially allyl chloride.
Preferred starting materials are compounds of formula III, IV or V in which Rl and R2 are
hydrogen and ~3 is methyl or, especially, hydrogen.
More especially preferred starting materials are compounds of formula III, IV or V in
which rn is 2, n is from 3 to 6, p is from 5 to 40, q is 0, A is a dinuclear radical of a bis-
phenol and Rl, R2 and R3 are hydrogen.
Either the starting material can be epoxidised with a solution of a dioxirane in a ketone, or
the dioxirane is prepared in situ in the reaction mixture with the starting material.
The preparation of dioxirane solutions is known ~ se and is described, for example, by
W. Adam et ah in J. Org. Chem., ~2, 2800-3 (19~7) and by R. Mello in J. Org. Chem., 53,
3890-1 (1988). ~or this purpose a peroxomonosulfate, for example potassium peroxo-
monosulfate, is added to a solution of a lcetone, especially an aliphatic ketone, such as
ace~one, hexafluoroacetone, methyl ethyl ketone or cyclohexanone, which has been ad-
justed with a buffer to a pH value of approximately from 6 to l0, especially from 6 to 8.
The resulting dioxirane can, if desired, be concentrated. The solution can be used as such
directly for the epoxidation, or can be stored for some time with cooling. The peroxo-
monosulfates used may be, for example, the alkali metal salts of peroxomonosulfuric acid
(Caro's acid), such as the sodium or potassium salts. F or example it is possible to use for
this purpose the product Oxone(~ produced by Du Pont. This is a mixture of potassium
peroxomonosulfate with potassium sulfate and potassium hydrogen sulfate.
The epoxidation of aromatic allyl ethers with dioxirane solutions can be carried out, for
example, as follows:
The starting material is introduced into a vessel as such or in a solvent that is inert under
the reaction conditions, and the dioxirane solution in the respective ketone is added.
Generally, approximately from one to twenty mols of dioxirane is used per mol of double
bond to be epoxidised. The addition of the dioxirane solution and the subsequent reac-
tion can be carried out with cooling or with heating of the reaction mixture to reflux.
Depending on the reactivity of the reactants and the temperatures employed, the epoxida-
tion normally takes from 0.5 to 24 hours.
'7~
The epoxidation of the arornatic allyl ether, in which the dioxirane is produced in situ in
the reaction mixture with the starting material, may be carried out, for example, as
follows:
The starting material is introduced as such, or in a solvent that is inert under the reaction
conditions, into a vessel together with a phase transfer catalyst and in conjunction with a
ketone, especially an aliphatic ketone, such as acetone, hexafluoroacetone, methyl ethyl
ketone or cyclohexanone, and water, so that a two-phase system results. The aqueous
phase contains a buffer for establishing the pH value in a range of approximately from 6
to 10, especially from 6 to 8. Subsequently a peroxomonosulfate, for example Oxone~',
is added. The amount of peroxomonosulfate is generally approximately from one to ten
mols per mol of double bond to be epoxidised. The peroxomonosulfate can be added in
solid form or dissolved in buffered water (pH value approximately from 6 to 10, depend-
ing on the pH value in the two-phase system). It is advisable to monitor the pH value of
the reaction rnixture during the addition and keep it constant, if necessary by the addition
of a base, such as sodium hydroxide solution or potassium hyclroxide solution. Depend-
ing on the reactivity of the reactants and the temperatures employed, the epoxidation
normally takes from 0.5 to 24 hours.
In this variant it is possible to use any phase transfer catalyst that is known ~ se. There
are especially used crown ethers, such as 18-crown-6, or quaternary ammonium or phos-
phonium salts, such as tetrabutylammollium hyclrogell sulfate or tetrabutylphosphonium
hydrogen sulfate.
~ny buffer customary per se may be used as buffer solution. It is preferable to use pilOS-
phate buffers with which a pH value of approximately 7 is established.
Solvents for the starting material that are inert under the reaction conditions are, for
example, ~romatic hydrocarbons, which may optionally be halogenated, such as benzene,
toluene, xylenes, cumene, chlorobenzene or dichlorobenzene, or halogenated aliphatic
hydrocarbons, such as trichloroethane, tetrachloroethane, dichloromethane or chloro-
fonn, or esters, such as, for example, ethyl acetate.
The process of the invention can be carried out in air or under a protective gas, for
example nitrogen or argon.
- 6 -
Reaction temperatures of from 0 to 30C are preferred.
Especially preferred epoxidation reagents are bis-trifluoromethyldioxirane or, especially,
dimethyldioxirane.
In an especially preferred form of the process of the invention the aromatic allyl ether is
purified before the epoxidation step, for example by chromatography ~r, especially, by
distillation; higher-molecular-weight starting materials can be purified by thin-layer or
flash distillation. This process variant generally results in especially high yields and
epoxy values.
In another especially preferred form of the process of the invention, the epoxidation is
carried out in the manner described above in a two-phase system containing an aromatic
allyl ether, dissolved in an inert solvent, and an aqueous ketone phase, and the dioxirane
is produced in situ in the reaction mixture, the peroxomonosulfate being added in solid
forrn and the pH value being held constant by the addition of an aqueous solution of a
base, especially sodium hydroxide solution.
In this form of the process the pH value is preferably from 6.5 to 7.5, the aromatic allyl
ether is placed in a vessel in an inert solvent together with a crown ether or a quaternary
ammonium salt as phase transfer catalyst, and the ketone used is acetone.
The resins obtainable in accordance with the invention can be cured in a manner custom-
ary ~ se by adding a curing agent, for example a primary or secondary polyamine, an
anhydride of a polycarboxylic acid or o a catalytically-acting curing agent, such as a
tertiary amine, and if appropriate heating the cornposition. The cured products are
distinguished especially by a low halogen content.
The invention relates also to a process for the manufacture of cured producLs which com-
prises curing the epoxy resins obtainable in accordance with the process of the invention
by the addition of a curing agent known ~ se and, if appropriate, heating.
The curable mixtures can, if desired, contain further additives customary ~ se, such as
reactive diluents, plasticisers, extenders, fillers and reinforcing agents, for example
coaltar, bitumen, textile fibres, glass fibres, carbon fibres, mineral silicates, mica, quartz
powder, aluminium oxide hydrate, bentonite, wollastonite, kaolin, silicic acid aerogel or
2~ 97~7
metal powders7 such as aluminium powder or iron powder, and also pigments and dye-
stuffs, such as carbon black, oxide dyes and titanium dioxide, and also flame-proofing
agents, thixotropic agents, flOw agents (some of which can also be used as mould release
agents), such as silicones, waxes and stearates, or adhesion promoters, antioxidants and
light stabilisers.
The mixtures of the invention can be used very generally for the manufacture of cured
products and can be employed in a formulation adapted to the respective specific field of
application, in unfilled or filled state as a component of paint compositions, coating com-
positions, lacquers, moulding compositions, dipping resins, whirl sintering powders, in-
jection moulding folmulations, tool resins, powder lacquers, casting resins, impregnating
resins, laminating resins, adhesives or matrix resins.
The resins obtainable in accordance with the invention are suitable, for example, for use
in the fields of surface protection, laminating processes, in construction and especially in
electrotechnology and electronics. Compounds with an average of one epoxy group can
be used as reactive diluents.
Examples
~: Prepar~tioll of bisph~nol A-di~lycidyl ~ther
50 g (0.08 mol) of solid Oxone(~ are added over a period of three and a half hours at room
temperature, with vigorous stirring, to 15.4 g (0.05 mol~ of distilled bisphenol A-diallyl
ether (prepared according to DE-A-26 27 045) and 0.66 g of 18-crown-6 in a two-phase
system of 50 ml of acetone, 50 ml of dichloromethane and 100 ml of phosphate buffer pH
7.0, the pH being held constant with 15 % NaOH solution. After a further 15 minutes, the
phases are separated, 10 ml of acetone, 5 ml of dichloromethane, 100 ml of phosphate.
buffer pH 7.0 and 0.66 g of 1 8-crown-6 are added to the organic phase and, over a period
of three and a half hours, a further 50 g (0.08 mol) of solid Oxone(~) is added. After 15
minutes the phases are separated again and the above- described operations are repeated,
30 g (0.05 mol) of Oxone(g) being used. The reaction mixture is then extracted twice with
100 ml of toluene each time, and the combined organic phases are concentrated to 200 ml
using a rotary evaporator. The toluene phase is washed three times with 50 ml of lN
NaOH solution each time and five times with 50 ml of water each time, dried overMgSO4, filtered and concentrated by evaporation. 13.6 g (80 %) of a golden yellow
liquid having the following properties are obtained:
l~poxy number: 5.11 val/kg (87 %); l125:3730 mPa.s
total chlorine content: 425 ppm; hydrolysable chlorine
content: 128 ppm.
Example 2: Preparation of bisphenol A-di~yci(lyl ether
87 ml of a 0.1M solution of dimethyldioxirane in acetone [prepared according to
W. Adam et al., J. Org. Chem., 52, 2800-3 (1987)] are added at room temperature, under a
nitrogen atmosphere, to 0.31 g (1 mmol) of distilled bisphenol A-diallyl ether and stirred
for six hours. The solvent and the excess dimethyldioxirane are then distilled off using a
rotary evaporator. 0.33 ~ (97 %) of a faintly yellow, clear liquid with an epoxy number of
4.8 val/kg (82 %) is obtained.
Example 3: Preparation of bisphenol A-di-(2,3-epoxybutyl) ether
23 g (0.04 mol) of Oxone(~ dissolved in 100 ml of phosphate buffer pH 7.0 are added
dropwise at room temperature, over a period of one and a quarter hours, to 3.36 g (0.01
mol) of distilled bisphenol A-dicrotyl ether (prepared analogously to the diallyl ether
according to DE-A-26 27 045) and 0.6 g of 18-crown-6 in a two-phase system of 50 ml of
acetone,50 ml of dichloromethane and 50 ml of phosphate buffer pH 7.0, the pH being
held constant with 15 % NaOH solution. Subsequently the reaction mixture is stirred for
a further one and a half hours and then extracted twice with 100 ml of dichloromethane
each time. The combined organic phases are washed t~ice with 50 ml of water eachtime, rendered free of peroxide over sodium sulfite, dried over MgSO4, filtered and con-
centrated by evaporation. 3.5 g (95 %) of a clear, light- brown liquid having an epoxy
number of 5.05 val/kg (93 %) are obtained.
Example 4: Preparation of bisphenol A~di-(2,3-epoxybutyl) ether
33 ml of a 0.15M solution of dimethyldioxirane in acetone are added at room temperature,
under a nitrogen atmosphere, to 0.17 g (0.5 mmol) of distilled bisphenol ~-dicrotyl ether
and stirred ~or one and three qu~rter hours. The solvent and the excess dimethyldiox*ane
are then distilled off in a rotary evaporator. 0.17 g (92 %) of a faintly yeliow, clear liquid
having an epoxy number of 4.9 val/kg (91 %) is obtained.
Example 5: P~epar~tion of poly-4-(2,3-epoxyblltoxy)-styrene
a) Preparation of poly-4-(2,3-butenoxy)-styrene.
107.7 g of K2CO3 are added over a period of 10 minutes at room temperature, with stir-
ring, to a solution of 60.1 g of Resin(~) M (poly-p-vinylphenol; Maruzen Oil) and 128.3 g
of crotyl chloride in 300 ml of l:)MSO and the reaction mixture is then stirred for four and
a half hours at 60C. The reaction mixture is then cooled, 300 ml of water are added and
extraction is carried out three times with 100 ml of ethyl acetate each time. The combined
organic phases are washed three times with 100 ml of water each time, dried overMgSO4, filtered and concentrated by evaporation. 82.8 g (95 %) of a brown resin are ob-
tained. l112~ = 1560 mPa.s.
b~ Preparation of poly-4-(2,3-epoxybutoxy)-styrene.
90 g (0.15 mol) of Oxone~ are added over a period of three and a quarter hours at room
temperature, with vigorous stirring, to 8.7 g of the polycrotyl ether of Example Sa) and
0.6 g of 18-crown-6 in a two-phase system of 50 ml of acetone, 50 ml of dichloromethane
and 10û ml of phosphate buffer pH 7.0, the pH value being held constant with 15 %
NaOH solution. The suspension is then stirred for a further hour and subsequently
filtered. The filtrate is extracted three times with 100 ml of methyl ethyl ketone each
time, the combined organic phases are washed twice with 100 ml of saturated NaClsolution each time, tested for peroxides with KI-starch paper, dried over MgSO4, filtered
and concentrated by evaporation. 9.0 g (95 %) of a brown resin are obtained.
60 = 780 mPa.s; epoxy number = 4.97 val/kg (95 %).
Example 6: Prepar~tion of bisphcnol F-di~lycidyl ether
100.1 g (0.5 mol) of bisphenol F and 133.9 g (1~75 mol) of allyl chloride are introduced
into 250 ml of DMSO, and 207.3 g (1.5 mol) of K2CO3 are added in portions over aperiod of one hour. The mixture is then heated to 60C and stirred for four hours at that
~emperature. The reaction mixture is subsequently cooled, poured onto 750 ml of water
and ext~acted three times with dichloromelhane. The combined organic phases are
washed three times with water, toluene is added and the whole is concen~rated by eva-
poration. 132 g of bisphenol F-diallyl ether are obtained in the forrn of a brown liquid. A
portion of this is distilled at 185C/1.3 Pa in a thin-layer evaporator. 14 g (0.05 mol) of
the distilled product are dissolved in a two-phase system of 50 ml of acetone,50 ml of di-
chloromethane and 100 ml of phosphate buffer pH = 7.0, and 0.66 g (2.5 rnmol) of18-crown-6 are added. Over a period of three and a half hours 60 g (95 mmol) of
Oxone~) are then added in portions at room temperature, the pH vallle being held constant
with 15 % NaOH. The phases are then separated, 30 ml of acetone, 5 ml of dichloro-
methane, 100 ml of phosphate buffer pH value 7.0 and 0.66 g (2.5 mmol) of 18-crown-6
are added to the organic phase, and, over a period of three and a half hours, a further 60 g
- lo -
(95 mmol) of Oxone(~) is added, with the pH value being held constant. The reaction mix-
ture is then diluted with water and extracted three times with dichloromethane. The
combined organic phases are washed once with lN NaOH and four times with water,
dried over MgSO4, filtered and concentrated by evaporation. 12.6 g of bisphenol
F-diglycidyl ether are obtained in the forrn of a clear brown liquid having an epoxy
content of 4.42 val/kg (75 %).
Exarnple 7: Preparation of a glycidyl ether of a cresol/formal(lehyde novolak
100 g (û.7 mol) of a cresol/formaldehyde novolak (Mn = 624; Mw = 906) and 11.8 g(0.035 mol) of tetrabutylammonium hydrogen sulfate are dissolved in 160.7 g (2.1 mol)
of allyl chloride at 30C, and then 1~0 g (3.5 mol) of NaOH are added in portions over a
period of one hour. The mixture is then heated to reflux and stirred for two hours at that
temperature. The reaction mixture is cooled, water is added, and extraction is carried out
three times with methyl ethyl ketone. The combined organic phases are washed three
times with 10 % N~14CI solution and twice with water, dried over MgSO4, filtered and
concentrated by evaporation. 126 g of the polyallyl ether of the cresol/formaldehyde
novolak are obtained in the forrn of a dark-violet highly viscous resin. 50 g of this crude
product are dissolved in as small a quantity as possible of ethyl acetate and filtered with
hexane/ethyl acetate = 1:1 through a 20 cm long silica gel column (diameter 10 cm). 45 g
of a light-yellow highly viscous resin are obtained. 19.1 g (û.1 mol) of the purifiedpro-
duct are dissolved in a two-phase system of 50 ml of acetonc, 50 ml of dichloromethane
and 100 ml of phosphate buffer pH = 7.0, and 0.66 g (2.5 mmol) of 18-crown-6 is added.
60 g (95 mmol) of Oxone~ are then added in portions at room temperature over a period
of three and a half hours, the pH value being held constant with 15 % NaOH. The phases
are then separated, 20 ml of acetone, 10 ml of dichloromethane, 5û ml of phosphate buffer
pH value 7.0 and 0.66 g (2.5 mmol) of 18-crown-6 are added to the organic phase, and a
~urther 60 g (95 mmol) of Oxone(~ is added in portions over a period of three and a half
hours with the pH value being held constant. The reaction mixture is then diluted with
water and extracted three times with ethyl acetate. The combined organic phases are
washed once with lN NaOH and three times with water, toluene is added and the whole
is concentrated by evaporation. 12 g of the polyglycidyl ether of the cresol/formaldehyde
novolak are obtained in the form of a brown solid with an epoxy content of 3.94 val/kg
(82 %)
