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Claims  |
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I claim:
1. The process of producing an epoxide polymer, comprising:
forming an essentially solventless mixture, fluid at room temperature,
consisting essentially of
1. at least one epoxidic prepolymer material having an epoxy equivalent
weight below 200, constituting between about 10% and 85% of the weight of
the epoxidic materials in the mixture, and selected from the group
consisting of
A. an epoxy resin prepolymer consisting predominantly of the monomeric
diglycidyl ether of bisphenol A,
B. a polyepoxidized phenol novolak or cresol novolak,
C. a polyglycidyl ether of a polyhydric alcohol, and
D. a diepoxide of a cycloalkyl or alkylcycloalkyl hydrocarbon or ether,
2.
2. an epoxidic ester having two epoxycycloalkyl groups and constituting at
least about 15% of the weight of the epoxidic materials in the mixture,
and
3. radiation-sensitive catalyst precursor which decomposes upon exposure to
electron beam or electromagnetic irradiation to provide a Lewis acid
effective to initiate polymerization of said epoxidic materials in said
mixture;
applying a portion of the mixture so formed to a substrate
and subsequently exposing said mixture on the substrate to electron beam or
electromagnetic irradiation to effect substantial polymerization of said
epoxidic materials. 2. The process of claim 1 for producing an epoxide
polymer, in which said catalyst precursor as present upon forming said
mixture constitutes between 0.1% and 5% of the weight of the mixture.
3. The process of claim 1 for producing an epoxide polymer, in which said
catalyst precursor as mixed with said epoxidic materials constitutes
between about 0.5% and about 2% of the weight of the resulting mixture.
4. The product produced by the process of claim 1.
5. The process of producing an epoxide polymer, comprising:
forming an essentially solventless mixture, fluid at room temperature,
consisting essentially of
1. at least one epoxidic prepolymer material having an epoxy equivalent
weight below 200, constituting between about 10% and 85% of the weight of
the epoxidic materials in the mixture, and selected from the group
consisting of
A. an epoxy resin prepolymer consisting predominantly of the monomeric
diglycidyl ether of bisphenol A,
B. a polyepoxidized phenol novolak or cresol novolak,
C. a polyglycidyl ether of a polyhydric alcohol, and
D. a diepoxide of a cycloalkyl or alkylcycloalkyl hydrocarbon or ether,
2. an epoxidic ester having two epoxycycloalkyl groups and constituting at
least about 15% of the weight of the epoxidic materials in the mixture,
3. a monoepoxide having a viscosity at 23.degree.C of less than 20
centipoises and constituting up to about 15% of the weight of the epoxidic
materials in the mixture, and
4. a radiation-sensitive catalyst precursor which decomposes upon exposure
to electron beam or electromagnetic irradiation to provide a Lewis acid
effective to initiate polymerization of said epoxidic materials in said
mixture;
applying a portion of the mixture so formed to a substrate;
and subsequently exposing said mixture on the substrate to electron beam or
electromagnetic irradiation to effect substantial polymerization of said
epoxidic materials.
6. The product produced by the process of claim 5.
7. The process of claim 5 for producing an epoxide polymer, in which the
catalyst precursor as present upon forming said mixture constitutes
between 0.1% and 5% of the weight of the mixture.
8. The process of claim 5 for producing an epoxide polymer, in which the
cationic initiator in said mixture is a radiation-sensitive catalyst
precursor in the form of an aromatic diazonium salt of a complex
halogenide, which decomposes upon said exposure to irradiation to release
a halide Lewis acid effective to initiate substantial polymerization of
the epoxidic materials in the mixture.
9. The process of claim 8, in which said catalyst precursor as mixed with
said epoxidic materials constitutes between 0.1% and 5% of the weight of
the resulting mixture.
10. The process of claim 9, in which said catalyst precursor as mixed with
said epoxidic materials constitutes between about 0.5% and about 2% of the
weight of the resulting mixture.
11. The process of claim 5 for producing an epoxide polymer, in which the
catalyst precursor in said mixture is a radiation-sensitive catalyst
precursor in the form of p-chlorobenzenediazonium hexafluorophosphate.
12. The process of claim 5 for producing an epoxide polymer, in which the
catalyst precursor in said mixture is a radiation-sensitive catalyst
precursor in the form of 2,5-diethoxy-4-(p-tolylthio)benzenediazonium
hexafluorophosphate.
13. The process of claim 5 for producing an epoxide polymer, in which the
epoxidic prepolymer material in said mixture is made up in major part of
an epoxy resin prepolymer consisting substantially of the monomeric
glycidyl ether of bisphenol A.
14. The process of claim 13, in which the epoxidic prepolymer material in
said mixture consists of an epoxy resin prepolymer in the form
substantially of the monomeric glycidyl ether of bisphenol A.
15. The process of claim 5 for producing an epoxide polymer, in which the
epoxidic prepolymer material in said mixture is made up in major part of a
polyepoxidized phenol novolak or cresol novolak.
16. The process of claim 15, in which the epoxidic prepolymer material in
said mixture consists of a polyepoxidized phenol novolak or cresol
novolak.
17. The process of claim 5, in which the epoxidic prepolymer material in
said mixture consists of a polyglycidyl ether of a polyhydric alcohol.
18. The process of claim 5, in which the epoxidic prepolymer material in
said mixture consists of a diepoxide of a cycloalkyl or alkylcycloalkyl
hydrocarbon or ether.
19. The process of claim 5 for producing an epoxide polymer, in which said
ester having two epoxycycloalkyl groups in said mixture is
(3,4-epoxycyclohexyl)methyl 3,4-epoxycyclohexanecarboxylate.
20. The process of claim 5 for producing an epoxide polymer, in which said
ester having two epoxycycloalkyl groups in said mixture is
bis[(3,4-epoxy-6-methylcyclohexyl)methyl] adipate.
21. The product produced by the process of claim 8.
22. The process of producing a coated or imprinted paper product,
comprising:
forming an essentially solventless mixture, fluid at room temperature,
consisting essentially of
1. at least one epoxidic prepolymer material having an epoxy equivalent
weight below 200, constituting between about 10% and 85% of the weight of
the epoxidic materials in the mixture, and selected from the group
consisting of
A. an epoxy resin prepolymer consisting predominantly of the monomeric
diglycidyl ether of bisphenol A,
B. a polyepoxidized phenol novolak or cresol novolak,
C. a polyglycidyl ether of a polyhydric alcohol, and
D. a diepoxide of a cycloalkyl or alkylcycloalkyl hydrocarbon or ether,
wherein the sum of the weights of any such polyglycidyl ether of a
polyhydric alcohol (C) and of any such diepoxide of a cycloalkyl or
alkylcycloalkyl hydrocarbon or ether (D) present does not exceed about 10%
of the total weight of said epoxidic prepolymer materials present,
2. an epoxidic ester having two epoxycycloalkyl groups and constituting at
least about 15% of the weight of the epoxidic materials in the mixture,
3. a monoepoxide having a viscosity at 23.degree.C of less than 20
centipoises and constituting up to about 15% of the weight of the epoxidic
materials in the mixture, and
4. a radiation-sensitive catalyst precursor which decomposes upon exposure
to electron beam or electromagnetic irradiation to provide a Lewis acid
effective to initiate polymerization of said epoxidic materials in said
mixture;
applying on letterpress apparatus a portion of the mixture so formed to at
least predetermined areas of the surface of a paper substrate;
and subsequently exposing said mixture on the paper substrate to electron
beam or electromagnetic irradiation to release said Lewis acid in
sufficient amounts to effect substantial polymerization of said epoxidic
materials.
23. The coated or imprinted paper product produced by the process of claim
22.
24. The process of producing an epoxide polymer coated or imprinted on a
substrate, comprising:
forming an essentially solventless mixture, fluid at room temperature,
consisting essentially of
1. at least one epoxidic prepolymer material having an epoxy equivalent
weight below 200, constituting between about 10% and 85% of the weight of
the epoxidic materials in the mixture, and selected from the group
consisting of
A. an epoxy resin prepolymer consisting predominantly of the monomeric
diglycidyl ether of bisphenol A,
B. a polyepoxidized phenol novolak or cresol novolak,
C. a polyglycidyl ether of a polyhydric alcohol, and
D. a diepoxide of a cycloalkyl or alkylcycloalkyl hydrocarbon or ether,
wherein the sum of the weights of any such polyglycidyl ether of a
polyhydric alcohol (C) and of any such diepoxide of a cycloalkyl or
alkylcycloalkyl hydrocarbon or ether (D) present does not exceed about 10%
of the total weight of said epoxidic prepolymer materials present,
2. an epoxidic ester having two epoxycycloalkyl groups and constituting at
least about 15% of the weight of the epoxidic materials in the mixture,
3. a monoepoxide having a viscosity at 23.degree.C of less than 20
centipoises and constituting up to about 15% of the weight of the epoxidic
materials in the mixture; and
4. a radiation-sensitive catalyst precursor which decomposes upon exposure
to electron beam or electromagnetic irradiation to provide a Lewis acid
effective to initiate polymerization of said epoxidic materials in said
mixture;
applying on a dry offset press a portion of the mixture so formed to at
least predetermined areas of the surface of said substrate;
and subsequently exposing said mixture on the substrate to electron beam or
electromagnetic irradiation to release said Lewis acid in sufficient
amounts to effect substantial polymerization of said epoxidic materials.
25. The coated or imprinted product produced by the process of claim 24.
26. The process of producing a coated or imprinted paper product,
comprising:
forming an essentially solventless mixture, fluid at room temperature,
consisting essentially of
1. at least one epoxidic prepolymer material having an epoxy equivalent
weight below 200, constituting between about 10% and 85% of the weight of
the epoxidic materials in the mixture, and selected from the group
consisting of
A. an epoxy resin prepolymer consisting predominantly of the monomeric
diglycidyl ether of bisphenol A,
B. a polyepoxidized phenol novolak or cresol novolak,
C. a polyglycidyl ether of a polyhydric alcohol, and
D. a diepoxide of a cycloalkyl or alkylcycloalkyl hydrocarbon or ether,
wherein the sum of the weights of any such polyglycidyl ether of a
polyhydric alcohol (C) and of any such diepoxide of a cycloalkyl or
alkylcycloalkyl hydrocarbon or ether (D) present does not exceed about 10%
of the total weight of said epoxidic prepolymer materials present,
2. an epoxidic ester having two epoxycycloalkyl groups and constituting at
least about 15% of the weight of the epoxidic materials in the mixture,
3. a monoepoxide having a viscosity at 23.degree.C of less than 20
centipoises and constituting up to about 15% of the weight of the epoxidic
materials in the mixture, and
4. a radiation-sensitive catalyst precursor which decomposes upon exposure
to electron beam or electromagnetic irradiation to provide a Lewis acid
effective to initiate polymerization of said epoxidic materials in said
mixture;
applying on a dry offset press a portion of the mixture so formed to at
least predetermined areas of the surface of a paper substrate;
and subsequently exposing said mixture on the paper substrate to electron
beam or electromagnetic irradiation to release said Lewis acid in
sufficient amounts to effect substantial polymerization of said epoxidic
materials.
27. The coated or imprinted paper product produced by the process of claim
26.
28. The process of producing a coated or imprinted paper product,
comprising:
forming an essentially solventless mixture, fluid at room temperature,
consisting essentially of
1. at least one epoxidic prepolymer material having an epoxy equivalent
weight below 200, constituting between about 10% and 85% of the weight of
the epoxidic materials in the mixture, and selected from the group
consisting of
A. an epoxy resin prepolymer consisting predominantly of the monomeric
diglycidyl ether of bispenol A.
B. a polyepoxidized phenol novolak or cresol novolak,
C. a polyglycidyl ether of a polyhydric alcohol, and
D. a diepoxide of a cycloalkyl or alkylcycloalkyl hydrocarbon or ether,
wherein the sum of the weights of any such polyglycidyl ether of a
polyhydric alcohol (C) and of any such diepoxide of a cycloalkyl or
alkylcycloalkyl hydrocarbon or ether (D) present does not exceed about 10%
of the total weight of said epoxidic prepolymer materials present,
2. an epoxidic ester having two epoxycyloalkyl groups and constituting at
least about 15% of the weight of the epoxidic materials in the mixture,
3. a monoepoxide having a viscosity at 23.degree.C of less than 20
centipoises and constituting from about 2% to about 15% of the weight of
the epoxidic materials in the mixture, and
4. a radiation-sensitive catalyst precursor which decomposes upon exposure
to electron beam or electromagnetic irradiation to provide a Lewis acid
effective to initiate polymerization of said epoxidic materials in said
mixture;
applying on a gravure press a portion of the mixture so formed to at least
predetermined areas of the surface of said paper substrate;
and subsequently exposing said mixture on the paper substrate to electron
beam or electromagnetic irradiation to release said Lewis acid in
sufficient amounts to effect substantial polymerization of said epoxidic
materials.
29. The coated or imprinted paper product produced by the process of claim
28.
30. The process of producing a coated or imprinted metal product,
comprising:
forming an essentially solventless mixture, fluid at room temperature,
consisting essentially of
1. at least one epoxidic prepolymer material having an epoxy equivalent
weight below 200, constituting between about 10% and 85% of the weight of
the epoxidic materials in the mixture, and selected from the group
consisting of
a polyglycidyl ether of a polyhydric alcohol and a diepoxide of a
cycloalkyl or alkylcycloalkyl hydrocarbon or ether,
2. an epoxidic ester having two epoxycycloalkyl groups and constituting at
least about 15% of the weight of the epoxidic materials in the mixture,
3. a monoepoxide having a viscosity at 23.degree.C of less than 20
centipoises and constituting up to about 15% of the weight of the epoxidic
materials in the mixture, and
4. a radiation-sensitive catalyst precursor which decomposes upon exposure
to electron beam or electromagnetic irradiation to provide a Lewis acid
effective to initiate polymerization of said epoxidic materials in said
mixture;
applying a portion of the mixture so formed to at least predetermined areas
of the surface of a metal substrate;
and subsequently exposing said mixture on the paper substrate to electron
beam or electromagnetic irradiation to release said Lewis acid in
sufficient amounts to effect substantial polymerization of said epoxidic
materials.
31. The coated or imprinted metal product produced by the process of claim
30.
32. The process of claim 1, in which said electromagnetic irradiation is
actinic irradiation.
33. The process of claim 1 in which said irradiation is electron beam
irradiation. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
Coating, printing, and related processes conventionally are carried out by
dissolving film-forming ingredients in a volatile solvent, applying the
resulting composition to a substrate, and drying and curing the
transferred material with or without heating, whereby the volatile solvent
is released to the atmosphere. Evolution of the solvent tends to lengthen
the hardening process and to leave voids and pinholes in the cured
coatings, making them porous. Emission of volatile solvents tends to
pollute the adjacent air unless costly arrangements are made to recover
practically all of the solvent, and release of flammable volatile solvents
may create fire and explosion hazards. Heating often is required to hasten
removal of the solvent, but the higher temperatures produced may damage
the substrate, or may cause running and deformation of the coating while
it still is soft.
Solvent-free mixtures of epoxide materials may be prepared based
essentially, for example, on certain epoxidic prepolymers such as the
reaction products of epichlorohydrin with bisphenol A or with novolaks.
Such prepolymers have been blended with various monoglycidyl ethers, or
with a glycol diglycidyl ether, primarily to modify the viscosity of the
prepolymer. Such mixtures can be shaped, as by coating, and then treated
with an activated cationic initiator to cure the resin. However, these
prepolymeric mixtures do not provide the rheological properties most
desirable for certain coating or related operations, or are unsuited for
application to various types of substrates. Coating and printing machines
require unique combinations of properties to permit smooth and rapid flow
of the coating and printing compositions through the machines for proper
application to the substrate web or sheets supplied to the machines. It
also has been observed that modification of the solvent-free epoxide
materials with socalled reactive diluents, such as monoglycidyl ethers, to
obtain the desired rheological properties tends to decrease the speed of
curing and to diminish the hardness of the material after initiation of
polymerization and curing, giving a more or less soft or tacky finish
rather than a tough, solid finish. Efforts to avoid this problem by the
inclusion of hardeners, such as amines, amides, or anhydrides, lead to
premature curing immediately upon mixing and a tendency to brittleness in
the cured material. It is an object of the present invention to provide
epoxide blends suitable for use in polymerizable compositions, and to
provide a related polymerizing process, which substantially avoid these
difficulties and disadvantages encountered with prior materials and
processes.
SUMMARY OF THE INVENTION
Accordingly, a new and improved blend of epoxide materials, fluid at room
temperature, consists essentially of at least one epoxidic prepolymer
material having an epoxy equivalent weight below 200, constituting between
about 10% and 85% of the weight of the blend, and selected from the group
consisting of an epoxy resin prepolymer consisting predominantly of the
monomeric diglycidyl ether of bisphenol A, a polyepoxidized phenol or
cresol novolak, a polyglycidyl ether of a polyhydric alcohol, and a
diepoxide of a cycloalkyl or alkylcycloalkyl hydrocarbon or ether; the
blend consists additionally of at least about 15% by weight of an epoxidic
ester having two epoxycycloalkyl groups, and from 0-15% by weight of a
monoepoxide having a viscosity at 23.degree.C of less than 20 centipoises.
Polymerizable compositions advantageously consist essentially of the
above-specified ingredients and a radiation-sensitive catalyst precursor
which decomposes upon application of energy to provide a Lewis acid
catalyst effective to initiate polymerization of the abovementioned
epoxidic materials. Such compositions are especially useful in providing
rapidly curable coatings, which may contain no more than a few percent by
weight of unpolymerizable materials. Thus, in accordance with the process
of the invention, an epoxidized polymer is produced by forming a mixture
of the epoxidic materials mentioned above and the catalyst precursor,
applying the mixture so formed to a substrate, and subsequently applying
energy to the mixture on the substrate to release the Lewis acid catalyst
in sufficient amounts to effect substantial polymerization of the epoxidic
materials.
DETAILED DESCRIPTION
There is provided and utilized, in accordance with the present invention, a
blend of epoxide materials which is fluid at room temperature. This blend
includes a material designated for convenience as a prepolymeric material,
which is described in detail hereinbelow. The blend also includes an ester
having two epoxycycloalkyl groups, designated for convenience as a
bis(epoxycycloalkyl) ester. The blend may include further, in limited
quantities, a monoepoxide material of specified maximum viscosity. To
provide a polymerizable composition, a cationic initiator is mixed or
dissolved in the blend.
Prepolymeric material. The blend of epoxide materials, fluid at room
temperature, contains at least one prepolymeric material having an epoxy
equivalent weight below 200 and selected from the group consisting of (A)
an epoxy resin prepolymer of the glycidyl-bisphenol A polyether type, (B)
a polyepoxidized phenol or cresol novolak, (C) a polyglycidyl ether of a
polyhydric alcohol, and (D) a diepoxide of a cycloalkyl or alkylcycloalkyl
hydrocarbon or ether. This epoxidic prepolymer material constitutes
between 10% and 85% of the weight of the blend.
Referring first to the resin prepolymer of the glycidyl-bisphenol A
polyether type, (A), the classic epoxy resin is obtained by the well known
reaction of epichlorohydrin (1-chloro-2,3-epoxypropane) and bisphenol A
(4,4'-isopropylidene-diphenol). The reaction product is believed to have
the form of a polyglycidyl or diglycidyl ether of bisphenol A (the
glycidyl group being more formally referred to as the 2,3-epoxypropyl
group) and thus may be thought of as a polyether derived from the diphenol
and glycidol ( 2,3-epoxy-1-propanol). The structure usually assigned to
the resinous product is
##SPC1##
In this formula the glycidyl groups having non-terminal positions in the
polymeric molecules become 2-hydroxytrimethylene groups, --CH.sub.2
CH(OH)CH.sub.2 --.
A viscous liquid epoxy resin, average molecular weight about 380, is
obtained by reacting the epichlorohydrin in high molecular proportion
relative to the bisphenol A, the reaction product containing well over 85
mole percent of the monomeric diglycidyl ether of bisphenol A (n = 0),
which may be named 2,2-bis[p-(2,3-epoxypropoxy)phenyl]propane, and smaller
proportions of polymers in which n is an integer equal to 1, 2, 3, etc.
The epoxy resin prepolymer utilized in accordance with the present
invention is a product of the kind just mentioned, consisting
predominantly of the monomeric diglycidyl ether of bisphenol A (probably
at least 80 mole percent of the monomer, although this proportion is
impractical to determine), having an average molecular weight below about
400, and having an epoxy equivalent weight in the range of 170 to 200,
usually about 172 to 187. Ref.: Handbook of Epoxy Resins, H. Lee and K.
Nevill, McGraw-Hill Book Company, 1967, pages 2-2 et seq. on "Synthesis of
Glycidyl-type Epoxy Resins", particularly pages 2-3 and 2-4 on the
synthesis of monomeric diglycidyl ether of bisphenol A.
Referring next to the phenol novolaks and cresol novolaks, (B), these
products are made, following procedures well known in the
phenol-formaldehyde resin art, by a condensation reaction involving
formaldehyde and a commercial grade of cresol (or phenol) in excess
amounts, using an acid catalyst, and yielding liquid or low-fusing
thermoplastic products. Such products are available in epoxidized forms,
having average molecular weights in the vicinity of 1,000 and epoxy
equivalent weights in the range of 160 to 200, frequently about 170-180.
Referring to the polyglycidyl ethers of polyhydric alcohols, (C), a readily
available example is the diglycidyl ether of 1,4-butanediol, also named
1,4-bis(2,3-epoxypropoxy)-butane, having the structural formula
##EQU1##
The epoxy equivalent weight of this compound when pure is 101.
Another diglycidyl ether of a glycol is diethylene glycol diglycidyl ether,
also named bis[2-(2,3-epoxypropoxy)-ethyl] ether, having an epoxy
equivalent weight of 109 and the structural formula
##EQU2##
A further example of a polyglycidyl ether of a polyol is a diglycidyl or
triglycidyl ether of glycerol; and triglycidyl ether is
1,2,3-tris(2,3-epoxypropoxy) propane, while the diglycidyl ethers are
2,3-bis(2,3-epoxypropoxy)-1-propanol and
1,3-bis(2,3-epoxypropoxy)-2-propanol. One readily available product is a
mixture of the triglycidyl ether with one or both of the diglycidyl
ethers, having an epoxy equivalent weight roughly midway between that of
the triglycidyl ether, 87, and that of the diglycidyl ethers, 102. It is
noted that the presence, for example, of the additional ether oxygen in
diethylene glycol diglycidyl ether, or of the remaining alcoholic hydroxy
group in the diglycidyl ethers of glycerol, does not detract from the
suitability of these compounds having rather low epoxy equivalent weights
as polyglycidyl ethers of polyols in the epoxide blends of the invention.
Referring to the diepoxides of cycloalkyl or alkylcycloalkyl hydrocarbons
or ehters, (D), these epoxidic compounds may be illustrated by the
following.
A diepoxide of an alkylcycloalkyl hydrocarbon is vinylcyclohexene dioxide,
more specifically identified as
3-(epoxyethyl)-7-oxabicyclo[[4.1.0]heptane, or 1,2-epoxy-
4-(epoxyethyl)cyclohexane, having an epoxy equivalent weight of 70 and the
structural formula
##EQU3##
A diepoxide of a cycloalkyl hydrocarbon is dicyclopentadiene dioxide, more
specifically identified as 3,4-8,9-diepoxytricyclo[5.2.1.0.sup.2,6
]decane, having an epoxy equivalent weight of 82 and the structural
formula
##EQU4##
A diepoxide of a cycloalkyl ether is bis( 2,3-epoxycyclopentyl) ether,
otherwise named 2,2'-oxybis (6-oxabicyclo-[3.1.0]hexane), having an epoxy
equivalent weight of 91 and the structural formula
##EQU5##
Bis(epoxycycloalkyl) ester. In addition to the epoxidic prepolymers
(designated A-D) discussed hereinabove, the blend of epoxide materials
includes also, admixed therewith, an ester having two epoxycycloalkyl
groups. This diepoxidic alicyclic ester constitutes at least about 15% of
the weight of the blend, and conveniently may be an ester of an epoxidized
cyclic alcohol and an epoxidized cycloalkanecarboxylic acid. Thus, a
suitable ester of epoxidized cyclohexanemethanol and epoxidized
cyclohexanecarboxylic acid is the diepoxide (3,4-epoxycyclohexyl)methyl
3,4-epoxycyclohexanecarboxylate; this same ester may be indexed under the
name 7-oxabicyclo[4.1.0]hept-3-ylmethyl
7-oxabicyclo[4.1.0]heptane-3-carboxylate, and has the formula
##EQU6##
Another suitable ester having two epoxycycloalkyl groups may be obtained
as an ester of an alkyl-substituted (epoxycycloalkane)methanol and a
dibasic acid, for example,
bis[(3,4-epoxy-6-methylcyclohexyl)methyl]adipate, which may be named
alternatively bis[(4-methyl-7-oxabicyclo[4.1.0]hept-3-yl) methyl] adipate,
and which has the formula
##EQU7##
Monoepoxide material. The epoxide blend additionally may include a
monoepoxide having a viscosity at 23.degree.C of less than 20 centipoises,
constituting not more than about 15% of the weight of the blend. Examples
of suitable monoepoxides are the following:
Propylene oxide (1,2-epoxypropane),
##EQU8##
Butylene oxide (1,2-epoxybutane),
##EQU9##
Allyl glycidyl ether (1-allyloxy-2,3-epoxypropane),
##EQU10##
Butyl glycidyl ether (1-butoxy-2,3-epoxypropane),
##EQU11##
Glycidyl phenyl ether (1,2-epoxy-3-phenoxypropane),
##EQU12##
It will be appreciated that more than one such monoepoxidic compound may be
utilized, provided that together these monoepoxides do not exceed the
specified proportion of the weight of the epoxide blend or of the
polymerizable composition. A readily available product is a mixture of
ethers of the structure
##EQU13##
where R is alkyl, that is, glycidyl alkyl ethers. One such mixture
contains predominantly glycidyl octyl ether and decyl glycidyl ether,
while another contains predominantly dodecyl glycidyl ether and glycidyl
tetradecyl ether.
Still another useful type of monoepoxide material is a polyolefin (e.g.,
polyethylene) epoxide. Such epoxides are exemplified by epoxidized, low
molecular weight by-products of the polymerization of ethylene, which may
be separated as mixtures high in 1-alkenes in the range from about 10 to
20 carbon atoms, that is from about 1-decene to about 1-eicosene.
Epoxidation then provides mixtures of the corresponding 1,2-epoxyalkanes,
examples being mixtures high in the 1,2-epoxy derivatives of alkanes
having 11 to 14 carbons, or having 15 to 18 carbons.
Initiator. The blend of epoxide materials may be utilized promptly upon
mixing for forming a body, film, or coating of desired shape and the
curing thereof effected at once or later, or both of the shaping and the
curing may be carried out at a later convenient time or different place. A
polymerization initiator may be mixed into the body in a form which is
immediately active, so that polymerization commences during the mixing and
is completed within a few minutes. For many shapes such mixing cannot be
achieved after carrying out the shaping, for example after making a
coating, and rapid polymerization would interfere with or prevent the
shaping. Accordingly, the initiator conveniently is mixed with the blend,
to form a polymerizable composition, with the initiator in an inactive
condition. Radiation-sensitive catalyst precursors are discussed
hereinbelow. Catalyst precursors ordinarily will be present in the
polymerizable compositions of the invention in amounts ranging from about
0.5% to about 2% of the total weight of the compositions less than 0.1% or
more than 5% seldom being called for. The presence of several percent by
weight, for example, of a catalyst precursor causes only a slight dilution
of the epoxidic materials of the composition, so that the approximate
limits specified hereinabove for the weight proportions of the various
epoxides in the epoxide blend ordinarily are not changed substantially,
when calculated as weight proportions of the entire composition, by the
addition of a catalyst precursor.
Suitable radiation-sensitive catalyst precursors decompose to provide a
Lewis acid upon application of energy. The energy required for effective
decomposition likewise may be energy applied by bombardment with charged
particles, notably by high-energy electron beam irradiation. However, the
catalyst precursors described hereinbelow are primarily photosensitive,
and the required energy is imparted by actinic irradiation, which is most
effective at those regions of the electromagnetic spectrum at which there
is high absorption of electromagnetic energy by the particular catalyst
precursor used. More than one of these types of energy may be applied to
the same system; e.g., ultraviolet light irradiation followed by electron
beam irradiation, and post-heating also may be employed, although
irradiation ordinarily can effect a suitable cure.
Preferred photosensitive Lewis acid catalyst precursors are aromatic
diazonium salts of complex halogenides, which decompose upon application
of energy to release a halide Lewis acid. The aromatic diazonium cation
may be represented generally as [Ar-N.sup.+.tbd.N], where the aryl group
Ar, which may be alkaryl hydrocarbon group, is bonded to the diazonium
group by replacing one of the hydrogen atoms on a carbon atom of the
aromatic nucleus, and where the aryl group ordinarily carries at least one
pendant substituent for greater stability of the cation. Thus the pendant
substituent may be alkyl, or another substituent, or both. The complex
halogenide anion may be represented by [MX.sub.n.sub.+m 09 .sup..sup.- m.
Thus, the photosensitive salt and its decomposition upon actinic
irradiation may be depicted as follows:
[Ar-N.sup.+.tbd.N].sub.m [MX.sub.n.sub.+m ].sup.-.sup.m hv .fwdarw. mAr-X +
mN.sub.2 + MX.sub.n, (I)
where X is the halogen ligand of the complex halogenide, M is the metallic
or metalloid central atom thereof, m is the net charge on the complex
halogenide ion, and n is the number of halogen atoms in the halide Lewis
acid compound released. The Lewis acid halide MX.sub.n is an electron pair
acceptor, such as FeCl.sub.3, SnCl.sub.4, PF.sub.5, AsF.sub.5, SbF.sub.5,
and BiCl.sub.3, which upon suitable irradiation of the diazonium complex
salt is released in substantial quantities and initiates or catalyzes the
polymerization process, wherein the monomeric or prepolymeric material is
polymerized or cured as the result of the actinic irradiation.
The catalyst precursors in the form of photosensitive aromatic diazonium
salts of complex halogenides may be prepared using procedures known in the
art. Thus, for example, chlorometallic halogenide complexes may be
prepared in accordance with the method set forth by Lee et al. in Journal
of the American Chemical Society, 83, 1928 (1961). Exemplifying a
procedure of general utility, arenediazonium hexafluorophosphates can be
prepared by diazotizing the corresponding aniline with NOPF.sub.6, made by
combining HCl and NaNO.sub.2 with subsequent addition of hydrogen
hexafluorophosphate (HPF.sub.6) or of a hexafluorophosphate salt, or they
can be prepared by addition of a hexafluorophosphate salt to another
diazonium salt to effect precipitation. As a further example, various
morpholinoaryl complexes, containing the group
##EQU14##
can be prepared either from the aniline derivative or by adding an aqueous
solution of a metal salt of the desired complex halogenide to a solution
of morpholinobenzenediazonium tetrafluoroborate.
An illustrative selection of aromatic diazonium salts of complex
halogenides is listed in Table I. Many of the salts listed have been found
to be well adapted or superior for use as latent photosensitive
polymerization initiators in the epoxide polymerization process and
polymerizable epoxidic compositions of the present invention, based on
thermal stability, on solubility and stability in the epoxy formulations
used, on photosensitivity, and on ability to effect polymerization with
the desired degree of curing after adequate actinic irradiation. Following
the name of each aromatic diazonium halogenide is its melting point or
decomposition temperature, in degrees centigrade, and wavelengths of
electromagnetic radiation, in nanometers, at which it exhibits absorption
maxima.
The melting points given in Table I were determined generally by the usual
visual capillary tube method; in most cases discoloration began below the
observed melting point temperature with frothing decomposition at that
temperature. In some cases melting points or exotherms were determined
also by differential thermal analysis under nitrogen gas, and the
temperatures so determined are given in parentheses. The wavelengths of
absorption maxima in the ultraviolet-to-visible range were determined with
the diazonium complex salt dissolved in acetonitrile.
TABLE I
__________________________________________________________________________
M.P., Abs'n Max.,
.degree.C.
nm.
__________________________________________________________________________
2,4-dichlorobenzenediazonium
62-64 259, 285, 360
tetrachloroferrate(III)
p-nitrobenzenediazonium tetra-
93-95 243, 257, 310,
chloroferrate(III) 360
p-morpholinobenzenediazonium
121.5 240, 267, 313, 364
tetrachloroferrate(III)
2,4-dichlorobenzenediazonium
190 285
hexachlorostannate(IV)
p-nitrobenzenediazonium hexa-
126 258, 310
chlorostannate(IV)
2,4-dichlorobenzenediazonium
152 285, 325-340
tetrafluoroborate (shoulder)
p-chlorobenzenediazonium hexa-
162-164 273
fluorophosphate
2,5-dichlorobenzenediazonium
dec. 140 264, 318
hexafluorophosphate
2,4,6-trichlorobenzenediazonium
240-250 294, 337
hexafluorophosphate
2,4,6-tribromobenzenediazonium
245-260 306
hexafluorophosphate
p-nitrobenzenediazonium hexa-
156 (178)
258, 310
fluorophosphate
o-nitrobenzenediazonium hexa-
161.5
fluorophosphate
4-nitro-o-toluenediazonium hexa-123
(138) 262, 319
fluorophosphate (2-methyl-4-nitro-
benzenediazonium hexafluorophosphate)
2-nitro-p-toluenediazonium hexa-
164-165 286
fluorophosphate (4-methyl-2-
nitro-benzenediazonium hexafluoro-
phosphate)
6-nitro-2,4-xylenediazonium hexa-
150 237, 290
fluorophosphate (2,4-dimethyl-
6-nitrobenzenediazonium hexa-
fluorophosphate)
p-morpholinobenzenediazonium hexa-
162 (181)
377
fluorophosphate
4-chloro-2,5-dimethoxybenzenedia-
168-169 243 (shoulder),
zonium hexafluorophosphate
(198-208)
287, 392
2,5-dimethoxy-4-morpholinobenzene-
Above 266, 396
diazonium hexafluorophosphate
135
2-chloro-4-(dimethylamino)-5-meth-
111 273, 405
oxybenzenediazonium hexafluoro-
phosphate
2,5-diethoxy-4-(p-tolylthio)ben-
147 (150)
223 (shoulder),
zenediazonium hexafluorophosphate
247, 357, 397
(2,5-diethoxy-4-(p-tolylmercapto)-
benzenediazonium hexafluorophosphate)
2,5-dimethoxy-4-(p-tolylthio)ben-
146 (155)
358, 400
zenediazonium hexafluorophosphate
2,5-dimethoxy-4'-methyl-4-biphenyl-
167 405
diazonium hexafluorophosphate
(2,5-dimethoxy-4-(p-tolyl)benzene-
diazonium hexafluorophosphate)
2,4',5-triethoxy-4-biphenyldiazonium
136 265, 415
hexafluorophosphate (2,5-diethoxy-
4-(p-ethoxyphenyl)benzenediazonium
hexafluorophosphate)
4-(dimethylamino)-1-naphthalenedia-
148 280, 310, 410
zonium hexafluorophosphate
p-nitrobenzenediazonium hexafluoro-
141-144 257, 310
arsenate(V) (161)
p-morpholinobenzenediazonium hexa-
162 257, 378
fluoroarsenate(V) (176-177)
2,5-dichlorobenzenediazonium hexa-
161-162.5
238, 358
fluoroantimonate(V)
p-nitrobenzenediazonium hexafluoro-
140-141 257, 308
antimonate(V)
p-morpholinobenzenediazonium hexa-
153 254, 374
fluoroantimonate(V) (177.5-180.5)
2,4-dichlorobenzenediazonium hexa-
178-180 279, 322 (shoulder)
chloroantimonate(V)
2,4-dichlorobenzenediazonium penta-
193.5-195
285, 313
chlorobismuthate(III)
o-nitrobenzenediazonium pentachloro-
166.5-168
285, 313
bismuthate(III)
__________________________________________________________________________
The cationic initiators or catalyst precursors listed hereinabove are
solids. It usually is possible to dissolve such ingredients in one or more
of the polymerizable ingredients making up the epoxide blend which is
utilized in the polymerizable compositions of the present invention.
However, it frequently is more convenient for mixing purposes to provide
such an ingredient for the mixing operation already dissolved in a
solvent. Thus the use of a small amount of a solvent medium such as
acetone or anisole often is convenient for introducing the solid additive
and facilitating its solution and distribution throughout the epoxide
blend. It has been found that commercial propylene carbonate (a cyclic
propylene ester of carbonic acid, probably identified as primarily
4-methyl-1,3-dioxolan-2-one) makes a good solvent for the aromatic
diazonium complex salts, and the propylene carbonate so used is completely
miscible with epoxy resins. For example, propylene carbonate may make up
between approximately 1 | | |
