Note: Descriptions are shown in the official language in which they were submitted.
I
BACKGROUND OF THE INVENTION
Allylic esters of phthalic acids and androids have
been prepared by a variety of standard esterifica~ion
procedures. For example, the reaction of allylic halides
with metal salts of phthalic acids has been described, in
both aqueous and an hydrous systems, usually in the
presence of a tertiary amine catalyst. This
esterification is a two-step reaction, requiring first the
preparation of the metal salt of phthalic acid and second
the reaction of the metal phthalate with the allylic
halide. The requirement in this process for initial
preparation of the phthalate salt from the phthalic acid,
before the actual esterification, is accompanied by
several disadvantages; in an hydrous systems the process of
preparing the an hydrous metal phthalate is ime-consuming
since the salt must be prepared in aqueous solution and
subsequently dried and requires special equipment due to
corrosion problems; if the metal phthalate is prepared and
used in aqueous medium, substantial decomposition of the
allylic halide in the subsequent esterification may occur
due to its instability in the presence of water, and there
is the economic disadvantage of requiring an additional
operation in the overall synthesis
In U. S. Patent 3,086,g85, to overcome the above
mentioned disadvantages, a new method of preparing allylic
halides is taught which provides for the direct reaction,
in one step' of a phthalate acid or android with an
allylic halide using an amine catalyst.
U. S. Patent 3,Q35,084 teaches synthesis of methallyl
phthalateJ from salts of phthalic acid using as well an
amine catalyst.
French Patent 1,372,~67 introduces a novel catalyst,
namely a copper halide, metallic copper mixture to effect
the synthesis of ally phthalate by the same reaction
.
-- 2 --
route of the above discussed patents, namely conversion ox
the phthalic acid or android to its salt via alkaline
neutralization and subsequent reaction with an ally
halide.
Ally esters of phthalic acids have found a variety of
uses as plasticizers, as chemical intermediates and as
taught, for example, in U. S. Patents 3,824,104, 3,376,139
and 3,891,695 as components of photosensitive compositions.
Furthermore, the halogenated allylic esters of
phthalic acids have found a variety of applications such
as in insecticide compositions, as light-stabilizers for
polyvinyl halide resins, and, additionally, these
compounds are useful in the preparation of polymers which,
due to the high halogen content, are flame-retardant in
nature. As an example of art documenting particularly the
last application, one may refer to U. S. Patent 4,105,~10
which teaches the imparting of flame-retardant properties
to curable vinyl unsaturated polymers by incorporation
therein of Delilah tetrabromophthalate. These halogenated
ally esters of phthalic acid may be made by a variety of
methods, e. g., by the reaction of a halogenated phthalic
android and an alcohol as described in U. S. Patent
2,462,601 by the reaction of the alkali metal salt of a
tetrahalophthalic acid and an alkyd alcohol as illustrated
in Us S. Patent 2,617,820, etc.
In response to the need for developing compositions
suited for the application as coating for electronic
circuitry, which incorporate two basic properties, namely
(a) that they be radiation curable and (b) what they be
fire-retardant, research programs have been devised which,
inter alias have focused on the aforediscussed
halogenated ally phthalic esters since these compounds
meet these two basic requirements
2~9~3~
These and other requirements have been met by the
flame-retardant photosensitive composition of the present
invention which is hereafter described.
SUMMARY OF THE Intention
The present invention embraces a novel photosensitive
composition which combines excellent W curability and very
good flame-retardant properties.
Disclosed herein are halogenated ally or methallyl
esters, i. e., pylons, which, in combination with polythiols
and optionally photo initiators and other additives, result
in screenable liquids which can be applied to electronic
circuit boards and cured with W light to hard fire-retardant
coatings.
The invention provides a flame-retardant, photo curable
composition comprising a liquid, chain-extended, thither-
containing allylic or methallylic tetrahalophthalate or a
mixture thereof, and a polythiol.
The invention further provides a process of forming a
liquid chain-extended thioether-containing allylic or
methallylic tetrahaloph~halate which comprises reacting a
solid member of the tetrahalophthalate group of the formula
where
X I (1) X~B~ Rl-R2~
25~ CC~2~C~2 I X~B~ R2 I
X COC~2C3~2 (3) X-Br; I 2~C~
X R2 (4) XsCl~ R1~2~
(5) X~C17 2~3 and
6 ) XDC~ Lo 3 I Eye
with a polythiol in an amount so as to provide I to 0.~5
equivalents SH/equivalent of car~on-to-carbon double bond in
the tetrahalvphthalate at a temperature in the range 60 to
150C.
ENTAILED DESCRIPTION CF~It~r INvrN~
It is an object of the present invention to drop a
W curable composition suitable for coatings for electronic
circuitry.
-- 4
It is a further object of the present invention Jo
develop W curable electronic circuit coatings which are
characterized by an acceptable degree of flame retardant
These and other objects will become obvious as the
description of the invention proceeds.
According to the present invention tetrahalophthalic
androids are converted to salts in base and reacted with
ally chloride anger ~e~hallyl chloride in the presence of
copper/cuprous chloride catalyst Jo give allyl/m2thallyl
tetrahalophthalate esters in high yield and purity.
- pa-
Z~;~96
Compounds covered by the present disclosure have the
following structure:
where
X O R (1) X=Br; Rl=R2=H
X n I I X=Br; Rl=R2=C~3
X CCH2C SHEA (3) Or ; R2=CH3
X R2 I X=Cl; Rl=R2=~
(5) X=C1, Rl=R2=C~3 and
(6) X=Cl; lo R2=CH3
While compound 1 is a known compound (taught in
U. S. Patent 4,105,710), compounds 2 through 6 are not
documented in the prior art. U. S. Patent 3,035,084,
while teaching preparation of the methallylic phthalate,
as in the case of compound 5, does not teach the
preparation of a halogenated methallylic phthalate, and,
furthermore, synthesis of any of these halogenated
compounds 1 through 6 by use of copper/cuprous chloride
catalyst and by the reaction method described is also not
disclosed in the prior art even though use of the catalyst
and the reaction method are known for synthesis of
non-halogenated phthalates as evidenced by the patents
; referred to under background of the Invention'.
These pylons, which are crystalline solids, are
prereacted with a substoichiometric amount of polythiol in
I the presence of a free radical thermal initiator, e. g.,
benzopinacol to give a liquid mixture. This mixture is
then formulated with additional polythiol and optionally a
photo initiator and other additives to make screenable
- liquids which can be applied to electronic circuit boards
. and cured with W light to hard fire-retardant coating.
The use of benzopinacol to prereact a pylon with a
substoichiometric amount of a pothole is disclosed in
Us S. Patent 4,020,233.
_ 5 _
I
Polythiols operable herein are simple or complex
organic compounds having a multiplicity of pendant or
terminally positioned ASH functional groups per average
molecule.
The polythiol must contain 2 or more ASH groups/
molecule and have a viscosity range of essentially 0 to
20 million centipoises (cups) at 70C as measured by a
Brook field Viscometer either alone or when in the presence
of an inert solvent, aqueous dispersion or plasticizer.
Operable polythiols in the instant invention usually have
molecular weights in the range of about 34 to about 20,000
and preferably, from about 100 to about 10,000.
The polythiols operable in the instant invention may
- be exemplified by the general formula R8-(SH)n where
n is at least 2 and R8 is a polyvalent organic moiety
free from reactive carbon-to-carbon unsaturation. Thus,
R8 may contain cyclic groupings and hotter atoms such as
N, P or O and primarily contains carbon-carbon, carbon-
hydrogen, carbon-oxygen or ~ilicon-oxygen containing chain
linkages free of any reactive carbon-to-carbon
unsaturation.
One class of polythiols operable herein are esters of
i thiol-containing acids of the formula ~S~Rg~COOH where
Rug is an organic moiety containing no reactive
carbon-to-carbon unsaturation with polyhydroxy compounds
of structure Rlo-(OH)n where Rio
moiety containing no reactive carbon-to-carbon
j unsaturation, and n is 2 or greater, These components
will react under suitable conditions to give a polythiol
having tune general structure:
R It --R
I/
Al
where Rug and Rio are organic moieties cuntainin~ no
I
reactive carbon-to-carbon unsaturation, and n is 2 or
greater.
Polythiols such as the aliphatic monomeric polythiols
methane ditniol, hexamethylene deathly, decamethylene
deathly, tolylene-2,4-dithiol and the like) are operable
herein. Examples of the polythiol compounds preferred
include, but are not limiter to, esters of thioglycilic
acid (HS-CH2COOH), alpha-mercaptopropionic acid
(HS-CH(CH3)-COOH and beta-mercaptopropionic acid
(HS-CH2CH2COO~) with polyhydroxy compounds such as
glycols, trios, tutorials, ponytails, hexaols and the
like. Specific examples of the preferred polythiols
include, but are not limited to, ethylene glycol
bis(thioglycolate), ethylene glycol bus (beta-mercapto-
preappoint), trimethylolpropane iris (thioglycolate),
trimethylolpropane tris-(beta-mercaptopropionate),
pentaerythritol tetrakis (thioglycolate) and
pentaerythritol tetrakis (beta-mercaptopropionate), all of
which are commercially available. A specific example of a
preferred polymeric polythiol is polypropylene ether
glycol bis(beta-mercaptopropionate~ which is prepared from
polypropylene-ether glycol ye. 9., Pluracol P2010,
! Wyandotte Chemical Corp.) and beta-mercaptopropionic acid
by esterification.
Polythiol terminated polyoxyalkylene polyols, such as
i trimethylolpropane tris-(3-mercapto-2-hydroxypropyl-
monooxypropyl~ ether and trimethylolpropane iris-
(3-mercapto-2-hydroxypropyl-dioxypropyl) ether, are also
operable. Furthermore, saturated alicyclic deathless, such
as 1,5-cyclooctanedithiol, 3,7,11-trimethyl-1,5-
cyclododecanedithiol, 4-hexyl-1,2-cyclohexanedithiol,
ethylcyclohexyl deathly and d-limonene deathly represent
commercially available deathless that are operable herein.
I
Additionally, polythiols operable herein to give cured
solid polythioether products with the pylon in the
presence of a photo initiator include the mercaptoester
derivatives of styrene-allyl alcohol copolymers set owlet in
U. S. Patent 3,904,499 and the isocyanurate containing
polythiols disclosed in U. S. Patent 3,~76,440 and liquid
thiol-terminated polymers made in accord with Us S.
Patent 3,258,495.
An example of the aforesaid latter type liquid they'll-
terminated polymer is CAPTURE 3-800, commercially
available from Diamond Shamrock Chemical Company.
In carrying out the reaction to transform the
crystalline solid pylons to a chain-extended, polythio-
ether containing liquid by reaction with a polythiol in
the presence of a free radical thermal initiator, the
amount of polythiol used is a substoichiometric amount.
sufficient polythiol must be used to convert the solid
crystalline pylon to liquid polythioether but care must
be exercised that no too much polythiol is added which
could increase viscosity too much or cause golfing. It
has been found that a range of 0~1 to 0.25 equivalents
SH/equivalent of double bond in the pylon is operable to
satisfy the aforesaid requirements. Following the chain
extending reaction, additional polythiol is added to the
I - system to supply the stoichiometric amount necessary to
react with the remaining carbQn-to-Carbon double bonds in
the chain-extended pylon optionally along with a
photo initiator for use as a photo curable composition.
The chain-extending reaction is performed at
temperatures above the melting point of the pylon and
the disassociation temperature of the free radical thermal
initiator. Temperatures in the range 60 to 150C are
usually employed.
* Trademark
-- 8
,
The free radical, thermal initiators used herein are
selected from substituted or unsubs~ituted pinnacles, ago
compounds, thrums, organic peroxides and mixtures
thereof.
S The organic peroxides operable are of the general
formula:
( 1 on
wherein n = 0 or 1, R is independently selected from
hydrogen aureole, alkyd, aureole carbonyl, alkaryl carbonyl,
aralkyl carbonyl and alkyd carbonyl and Al is alkyd or
aureole, said alkyd groups containing 1 to 20 carbon atoms.
Examples of operable organic peroxides include t but
are not limited tol2,5-dimethyl-2,5-di(t-butylperoxy)-
hexane, 1,3-bis(t-butylperoxyisopropyl)benzene, Boyce-
(cumylperoxyisopropyl)benzene, 2,4-dichloroben20yl
peroxide, caprylyl peroxide, laurel peroxide, t-butyl
peroxyisobutyrate, bouncily peroxide, p-chlorobenzoyl
peroxide, hydroxyheptyl peroxide, di-t-butyl doper-
phthalate, t-butyl pleracetate, t-butyl perbenzoate,
dicumyl peroxide t l,l-di(t-butylperoxy~-3,3,5 Tramiel-
cyclohexane and di-t-butyl peroxide.
Examples of ago compounds operable herein include, but
are not limited to, commercially available compounds such
as 2-t-butylazo-2-cyanopropanè; 2,?'-azobis~2~4-dimethyl-4-
methoxy-valeronitrile); 2,2'-azobis(isobutyronitrile);
2,2'-azobis(2,4-dimethylvaleronitrile) and l,l'-azobis-
(cyclohexanecarbonitrile~.
The thrums operable as thermal initiators herein are
of the formula:
I C-S-S C-N
I R4
wherein Al, R3, R3 and R4 taken singly can be
hydrogen, linear or branched alkyd having from 1 to about
12 carbon atoms, linear or branched alkenyl having from
2 to about 12 carbon atoms, cycloalkyl having from 3 to
about 10 ring carbon atoms, cycloalkenyl having from 3 to
about 10 ring carbon atoms, aureole having from 6 to about
12 ring carbon atoms, alkaryl having from 6 to about
12 ring carbon atoms, aralkyl having from 6 to about
12 ring carbon atoms and, when taken together, Al and
R2 and R3 and R4 can each be a diva lent alkaline
group (-CnH2n-) having from 2 to about 12 carbon
atoms, a diva lent alkenylene group (-CnH2n 2-) group
. having from 3 to about 10 carbon atoms, a diva lent
alkadienylene group -(CnH2n-4)- having from 5 to about
10 carbon atoms, a diva lent alkatrienylene group
-(C Ho 6)- having from 6 to about 19 carbon atoms, a
diva lent alkyleneoxyalkylene group (-CxH2xOLCxH2x-)
having a total of from 4 to about 12 carbon atoms or a
diva lent alkyleneaminoalkylene group:
( - CXH 2XNCX~ 2x
having a total of from 4 to about 12 carbon atoms.
Operable thrums include, but are not limited to,
tetramethylthiuram disulfide, tetraethylthiuram disulfide,
di-N-pentamethylenethiuram disulfide, tetrabutylthiuram
disulfide, dipehnyldimethylthiuram disulfide, diphenyl-
diethylthiuram disulfide and diethyleneoxythiuram
disulfide and the like.
I
The substituted or unsubstituted pinnacles operable
herein as a thermal initiator have the general formula:
RlP'3
R -C-C-R4
X Y
wherein Al and R3 are the same or different
substituted or unsubstituted aromatic radicals, R2 and
R4 are substituted or unsubstituted aliphatic or
aromatic radicals and % and Y which may be the same or
different are hydroxyl, alkoxy or airlocks.
Preferred pinnacles are those wherein Al, R2~ R3
and R4 are aromatic radicals, especially phenol radical
and X and Y are hydroxyl.
Examples of this class of compounds include, but are
not limited to, benzopinacol, 4,4'-dichlorobenzopinacol
4,4'-dibromoben~opinacol, 4/4'-diiodobenzopinacol,
4,4',4'l,4"'-tetrachlorobenzopinacol, 2,4,2l,4'-tetrachloro-
benzopinacol, 4,4'-dimethylbenzopinacol, 3,3'-dimethyl-
benzopinacol~ 2~2'-dimethylbenzopinacol, twitter-
methylbenzopinacol, 4,4'-dimethoxybenzopinacol,
4,4.,4 n 4 n -tetramethoxybenzopinacol, 4,4'-diphenyl-
benzopinacol, 4,4'-dichloro-4~,4"'-dime~hylbenzopinacol,
4,4'-dimethyl-4",4"'-diphenylbenzopinacol~ xanthonpinacol,
fluorenonepinacol, acetophenonepinacol, 4,4'-dimethylaceto-
phenone-pinacol, 4~4'~dichloroacetophenonepinacol,
1,1,2-triphenyl-propane-1,2-diol, 1,2,3,4-~etraphenyl-
butane-2,3-diol, 1,2-diphenylcyclobutane-1,2-diol,
propiophenone-pinacol r 4 4'-dimethylpropiophenone- -
pinnacle, 2,2'-ethyl-3,3'-dimethoxypropiophenone-pinacol,
1,1,1,4,4,4-hexafluoro-2,3-diphenyl~butane-2,3-dioof.
i99~
As further compounds according to the present
invention, there may be mentioned: benzopinacol-mono-
methyl ether, benzopinacol-mono-phenylether, benzopinacol
and monoisopropyl ether, benzopinacol monoisobutyl ether,
benzopinacol moo (diethoxy methyl) ether and the like.
The aforementioned free radical, thermal initiators
are added to the composition in amounts ranging from 0.01
- 1.0% by weight based on the weight of the pylon and
polythiol.
The compositions of the present invention may, if
desired, include such additives as antioxidant,
accelerators, dyes, inhibitors, activators, fillers,
pigments, antistatic agents, flame-retardant agents,
thickeners, thixotropic agents, surface-active agents,
viscosity modifies, extending oils, plasticizers,
tackifiers and the like within the scope of this
invention. Such additives are usually preblended with the
ethylenically unsaturated compound or polythiol prior to
or during the compounding step. Operable fillers include
natural and synthetic resins, carbon black, glass fibers,
- wood flour, clay, silica alumina, carbonates, oxides,
hydroxides, silicates, glass flakes, glass beads, borate,
phosphates, diatomaceous earth, talc, kaolin, barium
sulfate, calcium sulfate, calcium carbonate, antimony
oxide and the like. The aforesaid additives may be
present in quantities up to 500 parts or more per
100 parts of ethylenically unsaturated compound and
polythiol by weight and preferably about 0.005 to about
300 parts on the same basis.
The curing reaction to form hard, fire-re~ardant
coatings on substrates is preferably but not necessarily,
carried out in the presence of a photo initiator. Various
photo initiators operable herein include, but are not
- 12 -
limited to, benzophenone, acetophenone, o-methoxybenzo-
phenone, acenapthene-quinone, methyl ethyl kitten,
valerophenone, hexanophenone, alpha-phenylbutyrophenone,
p-morpholinopropiophenone, dibenzosuberone, 4-morpholino-
benzophenone, 4'-morpholinodeoxybenzoin, p-diacetyl-
Bunsen, 4-aminobenzophenone, 4'-methoxyacetophenone,
benzaldehyde, alpha-tetralone, 9-acetylphenanthrene,
2-acetylphenanthrene, 10-thioxanthenone, acutely-
phenanthrene, 3-acetylindole, 9-fluorenone, Linda none
1j3,5-triacetylbenzene, thioxanthen-9-one, xanthrene-
9-one, 7 H-benz[de]anthracen-7-one, l-naphthalaehyde,
4,4'-bis(dimethylamino) benzophenone, fluorene-9-one,
l'-acetonaphthone, 2'-acetonaphthone, buttondown,
triphenylphosphine, tri-o-tolyphosphine, acetonaphthone,
buttondown, benz[a]anthracene-7.12-dione, etch
Another class of photosensitizes is the Bunsen ethers,
such as Bunsen methyl ether, Bunsen ethyl ether, Bunsen
isopropyl ether and Bunsen isobutyl ether. The
photosensitizes are usually added in an amount ranging
from 0.0005 to 30~ by weight of the ethylenically
unsaturated compound and the polythiol.
In addition, the halogenated ally compound in the
composition of this invention can act as its own
photo initiator, without added photo initiator of the above
types.
When US radiation is used, an intensity of 0.0004 to
60.0 watts~cm in the 250-400 nanometer region is
usually employed.
The curing reaction can alto be accomplished by using
high energy ionizing radiation at a dose rate in the range
0.00001 to 1,000 megarads/second.
The amount of ionizing radiation which is employed in
curing in the instant invention can vary between broad
limits. Radiation dosages of less than a megarad up to
- 13 -
10 megarads or more for electrons are operable; preferably
0002 to 5 megarads energy absorbed are employed.
The following examples will aid to explain, but
specifically not limit, the subject invention unless,
otherwise noted, all parts and percentages are by weight.
Example 1
Synthesis of Delilah Tetrabromophthalate (DATBP)
A mixture of 464 g tetrabromophthalic android, 80 9
sodium hydroxide, 650 ml water, 0.04 g copper powder, 2 9
cuprous chloride and 306 g ally chloride was stirred
2 hours at 70C to give 528 g (94~) Delilah te~rabromo-
phthalate. The pi was kept between 6.5 and 7.5 by adding
sodium hydroxide solution during the reaction.
Example 2
Dimethallyl tetrabromophthalat~ (DMATBP) was
synthesized in a similar manner as set out in Example 1 by
using methallyl chloride in place of ally chloride.
Example
A mixture of ally methallyl tetrabromopnthalate,
- 20 DATBP and DMATBP was synthesized in a similar manner as
set out in Example 1 by using a mixture of methallyl
chloride and ally chloride.
Delilah tetrachlorophthalate was synthesized by the
same procedure in Example 1 using te~rachlorophthalic
android in place of tetrabromophthal~c android.
Example 5
A mixture of 5~G g Delilah tetrabromophthalat~ 5.25 g
of dimethallyl tetrabromophthalate, 10.0 g Delilah
tetrachlorophthalate, 2.4 g ethylene glycol
bis-(3-mercaptopropiona~e) and 0.16 g benzopinacol was
heaved for 30 minute at 110C to form a chain-extended,
liquid polymer. Thereafter at awoke, 9.1 g ethylene
glycol byway mercaptopropionate) and 9.52 g of finely
divided hydrated alumina HYDRA 710 from Alcoa) was added
and mixed.
This formulation was shown to screen-print well, to
photo cure fast and to exhibit good solder resistance and,
S most importantly, testing of 2 ten-mil thick films have
revealed it to be flame-retardant as reflected by an
average Oxygen Index of 29.
In general, flame retardancy is measured by ASTM
Method D 2863-74 for oxygen index; an oxygen index of
about 27-28 or higher is considered generally acceptable.
While suitable for application to electronic circuit
boards, other applications for this composition may be
easily envisaged where radiation curable fire-retardant
coatings are required.
Variations may be made in materials, proportions and
procedures without departing from the scope of this
invention.
Example 6
2.09 g of Delilah tetrabromophthalate from Example l
and 0.91 g of pentaerythritol tetrakis(beta-mercapto-
preappoint) were mixed in a 13 mm test tube and slowly
melted at 80-85C to a clear solution The solution was
transferred to a glass plate and spread as a 20 mix thick
film thereon. The film was exposed to W radiation from a
Ferry W lamp for l minute. A solid, cured film resulted.
Example 6 was repeated except that a photo initiator,
i. e., 0.03 g of 2,2-dimethoxy-2-phenylacetophenone, was
added to the system. solid, cured film resulted.
example 8
Example 6 way repeated except that a photo initiator,
it e., 0.03 g of dibenzosuberone, was added to the
system. A solid, cured film resulted
I
Example 9
Example 6 was repeated except that a photo initiator,
i. e., 0.03 g of 4,4'-dimethoxybenzophenone, was added to
the system. A solid, cured film resulted.
Example 10
example 6 was repeated except that a photo initiator,
i. e., 0.03 9 of benzophenone, was added to the system. A
solid, cured film resulted.
Example 11
Example 6 was repeated except that Owe g of buoyancy-
pinnacle was added to the original mixture and, after
formation ox the thioether-containing chain-extended
pylon, 0.03 9 of 2,2-dime~hoxy-2-phenylacetophenone was
added prior to irradiation. A solid cured film resulted.
Example 12
A mixture of 20.48 g of Delilah tetrachlorophthalate,
2.06 g pentaerythritol tetrakis(beta-mercaptopropionate)
and 0.01 g benzopinacol were heated with stirring at 125C
for 1 hour to form a chain-extended, liquid polymer. The
polymer was cooled to 60C and 3.26 g of 2,2-dimethoxy-2-
phenylacetophenone, 0.03 g of pyrogallol and OOZE g of
phosphorous acid were added to the system along with
10.28 9 of pentaerythritol tetrakis(beta Marquette-
preappoint). This admixture was spread as a 20 mix thick
coat on a glass plate and exposed to US radiation for
2 1/2 minutes. A solid, cured, transparent coating
adhering to the glass plate re~ultedQ
