[0001] This invention relates to photopolymerizable compositions and to a method employing
same. More particularly, this invention relates to the use of certain benzoyl benzoates
as photoinitiators for ethylenically unsaturated compounds.
[0002] Photopolymerization of unsaturated compositions wherein a photoinitiating compound
is included in the polymerizable mass is well known in the art. The process has many
advantages over thermal polymerization and is particularly useful where long holding
life combined with rapid hardening at low temperature is desirable. Photoinitiating
compounds must absorb light and utilize the energy so acquired to initiate polymerization.
[0003] A large number of compounds have been found useful as photoinitiators for the polymerization
of unsaturated compounds. Among those heretofore in most common usage in industry
are the benzoin ethers of primary and secondary alcohols such as methyl alcohol, ethyl
alcohol and isobutyl alcohol.
[0004] While particular industrial applications often dictate certain requisite characteristics,
the primary determinants of universal application in the selection of a suitable photoinitiating
compound are its level of reactivity and its effect upon storage stability when combined
with the photopolymerizable medium wherein it is to function. This latter characteristic
is significant in view of the desirability of one-component systems which will not
gel prior to use.
[0005] While compounds in common use as photoinitiators do effect rates of polymerization
which are industrially acceptable and render photopolymerization superior to thermal
polymerization in various applications, methods of achieving increased polymerization
rates with increased stability are constantly being sought. Improved photoinitiators
are particularly desirable since photopolymerization techniques are gaining increasingly
widespread acceptance due to the inherently lower equipment costs, reduction of volatile
emissions and reduced energy consumption which attend their use.
[0006] Thus, the ethers of benzoin, which are widely used as photoinitiating compounds,
are not wholly satisfactory with regard to the one-component system storage stability
factor. Any unsaturated system to which a benzoin ether is added has considerably
diminished dark storage stability and will gel prematurely. Various attempts have
been made to remedy this deficiency of the benzoin compounds by including stabilizing
additives in the polymerization system. Thus, U.S. Patent 3,819.495 discloses the
addition of organic chlorine containing compounds and copper compounds as a stabilization
system while U.S. Patent 3.819.496 teaches the use of organic chlorine compounds with
iron and/or manganese compounds for that purpose. Many other stabilizers have been
suggested and ; while some improvements have been achieved in the stability of unsaturated
systems containing benzoin-type photoinitiators, the necessity of incorporating stabilizing
additives raises the cost of such systems appreciably while the results are still
not wholly satisfactory.
[0007] Thus, various aromatic compounds have been proposed as photoinitiators for unsaturated
compounds. For example, U.S. Patent No. 3,715,293 teaches the use of acetophenone
compounds such as 2,2-diethoxyacetophenone, while a series of patents including U.S.
Patents 3,404,998 ; 3,926,638 ; 3,926,639; 3,926,640 ; 3,926,641 ; 4,022,674; 4,004,998
; 4,008,138 and 4,028,204 describe complex compounds derived from benzophenone. As
an example of the benzophenone-derived materials, U.S. Patent 3,404,998 describes
photoinitiators made by reacting carboxy-substituted benzophenones with hydroxyl-containing
polyethylenically unsaturated esters, while U.S. Patent 3,404,998 describes photoinitiators
made by reacting carboxy-substituted benzophenones with hydroxyl-containing polyethylenically
unsaturated esters, while U.S. Patents 3,926,639 and 4,028,204 describe a benzophenone
substituted with a carboxy group and an ester group which is reacted with certain
resins, such as alkyds, polyesters, polyethers, polyamides and epoxides, to provide
the photoinitiator.
[0008] Another approach is disclosed in U.S. Patent No. 3,759,807 where certain benzophenones
which must be used with activators are disclosed. Also representative of benzophenone
systems is Brit. Patent 1,223.463 which teaches the addition of diketones such as
m-benzoylbenzophenone, ethylene glycol bis (p-benzoylbenzoate) or diethylene glycol
bis (p-benzoylbenzoate) to nylon to give photosensitive materials suitable for the
preparation of printing plates.
[0009] In U.S. Patent No. 4,017,652, ethyl benzoylbenzoate is disclosed as a photosensitizer
which must be used in connection with a photoinitiator such as a benzoin ether.
[0010] With regard to rate of polymerization and the dark storage stability of the uncured
system, none of the most widely used photoinitiating compounds is wholly acceptable
in unsaturated systems.
[0011] Now it has been found in accordance with this invention that certain benzoyl benzoates
and benzamides are excellent photoinitiators for ethylenically unsaturated compounds.
These photoinitiators provide polymerizable systems not subject to premature gelation.
Furthermore, these photoinitiators are reactive in many different systems based on
ethylenically unsaturated compounds.
Summary of the invention
[0012] The photopolymerizable composition of this invention comprises an ethylenically unsaturated
compound and a p-benzoyl benzoate or a p-benzoyl benzamide. After applying the compositions
to the desired substrate, curing is effected by exposure to actinic radiation.
Detailed description of the invention
[0013] More in detail, the photopolymerizable composition of this invention comprises an
ethylenically unsaturated compound and a photoinitiating amount of a photoinitiator,
characterised in that said photoinitiator is a p-benzoyl benzoate or benzamide of
the formula :
wherein X is OR, NHR or NRR ; R is an independently selected hydrocarbon of 1 to 30
carbon atoms, alkoxysubstituted alkyl of 2 to 12 carbon atoms or aminosubstituted
alkyl of 2 to 12 carbon atoms ; R' is an independently selected halogen or X ; and
n and m are independently selected integers from 0 to 3.
[0014] In the foregoing definition, the term « hydrocarbon of from 1 to 30 carbon atoms
refers to straight and branched chain acyclic hydrocarbon groups which may contain
unsaturated carbon-to-carbon bonds.
[0015] Preferred compositions are characterized in that X is OR and R is an alkyl of 1 to
15, especially 1 to 13 carbon atoms, an alkenyl of 3 to 5 carbon atoms, an alkoxy-substituted
alkyl of 2 to 4 carbon atoms or an amino-substituted alkyl of 2 to 5 carbon atoms,
or are characterized in that X is the group NHR or NRR and R is an alkyl of 1 to 4
carbon atoms.
[0016] Illustrative compounds I include, but are not limited to, methyl-p-benzoylbenzoate
; tridecyl-p-benzoylbenzoate ; (2-propenyl)-p-benzoylbenzoate ; (3-pentenyl)-p-benzoyl-benzoate
; methoxymethyl-p-benzoylbenzoate ; (2-ethoxyethyl)-p-benzoylbenzoate ; aminoethyl-p-benzoylbenzoate
; (2-amino-propyl)-p-benzoylbenzoate ; (dimethylaminopropyl)-p-benzoylbenzoate ; N-methyl-p-benzoylbenzamide
; N-tridecyl-p-benzoylbenzamide ; N-(2-propenyl)-p-benzoylbenzamide; N-(3-pentenyl)-p-benzoylbenzamide
; N-methoxymethyl-p-benzoylbenzamide ; N-(2-ethoxyethyl)-p-benzoylbenzamide; N-aminoethyl-p-benzoylbenzamide
; N-(2-aminopropyl)-p-benzoylbenzamide; N-(dimethylaminopropyl)-p-benzoylbenzamide
; 4-butoxycarbonyl-4'-fluorobenzophenone ; 4-butoxycarbonyl-3-bromobenzophenone, 4-ethoxycarbonyl-3,4,4'-trichlorobenzophenone
and 4-butoxycarbonyl-4'-ethoxycarbonylbenzophenone.
[0017] The benzoyl benzoates and benzamides I are known compounds, some of which are commercially
available. Alternately, they are readily prepared by methods described in the literature.
Thus, for example, they can be prepared by the techniques described in Advanced Organic
Chemistry : Reactions, Mechanisms and Structure, J. March ed., McGraw Hill, New York
(1968). The esters can also be prepared by the procedure of D. Bichan and M. Winnik,
Tetrahedroh Letters, 3857 (1974).
[0018] The compositions curable by actinic radiation according to the invention can contain
a photopolymerizable polymer in a reactive ethylenically unsaturated monomeric medium,
a reactive polymer alone, a reactive monomer alone, or any of these combined with
an inert solvent. Additionally, the polymerizable composition can contain any of the
pigments commonly used in photopolymerization techniques.
[0019] Polymerizable ethylenically unsaturated compounds which are useful in practicing
the invention are acrylic, a-alkacrylic and a-chloroacrylic acid compounds such as
esters, amides and nitriles. Examples of such compounds are acrylonitrile, methacrylonitrile,
methyl acrylate, ethyl acrylate, methyl methacrylate, isobutyl methacrylate, 2-ethylhexyl
acrylate, methacrylamide and methyl a-chloroacrylate. Also useful, although not preferred
due to their slower rates of reactivity, are vinyl and vinylidene esters, ethers and
ketones. Additionally, compounds having more than one terminal unsaturation can be
used. Examples of these include diallyl phthalate, diallyl maleate, diallyl fumarate,
triallyl cyanurate, triallyl phosphate, ethylene glycol dimethacrylate, glycerol trimethacrylate,
pentaerythritol triacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate,
methacrylic anhydride and allyl ethers of monohydroxy or polyhydroxy compounds such
as ethylene glycol diallylether and pentaerythritol tetraallyl ether tetraallyl. Nonterminally
unsaturated compounds such as diethyl fumarate can similarly be used.
[0020] The acrylic acid derivitives are particularly well suited to the practice of the
invention and are consequently preferred components as monomers in monomer-containing
polymerizable systems and as reactive centers in polymerizable polymers. While monomeric
styrene can be used in the practice of the invention, it is not a preferred constituent
of systems polymerizable thereby due to its slow rate of reaction.
[0021] Additionally, the photopolymerizable composition can contain a sensitizer capable
of enhancing the photoinitiating reactivity of the photoinitiating compound of the
invention by triplet sensitization. Examples of sensitizers useful in the practice
of the invention are such compounds as biphehyl, xanthone, thioxanthone and acetophenone.
These are typically added in amounts ranging from 0,1 to 6 weight percent. The techniques
whereby such sensitizers are selected for use in conjunction with particular photoinitiators
are well known in the art. See, for example, MUROV, Handbook of Photochemistry, Marcel
Dekker, Inc., New York (1973).
[0022] Additionally polymerization promoters such as organic amines can be used to accelerate
cure rates, either alone or in combination with a sensitizer. Such amines can be primary,
secondary, or preferably, tertiary, and can be represented by the general formula
:
wherein R' and R
2 are independently selected hydrogen, straight chain or branched alkyl having from
1 to about 12 carbon atoms, straight chain 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 atoms, aryl having from 6 to about 12 ring carbon atoms,
alkaryl having 6 to about 12 ring carbon atoms ; R
3 has the same meaning as R' and R
2 with the exception that it cannot be hydrogen and that it cannot be aryl when both
R' and R
2 are aryl. Also, when taken together R
2 and R
3 can be divalent alkylene groups having from 2 to about 12 carbon atoms, a divalent
alkenylene group having from 3 to about 10 carbon atoms, a divalent alkadienylene
group having from 5 to about 10 carbon atoms, a divalent alkatrienylene group having
from 5 to about 10 carbon atoms, a divalent alkyleneoxyalkylene group having a total
of from 4 to about 12 carbon atoms, or a divalent alkyleneaminoalkylene group having
a total of from 4 to about 12 carbon atoms. As previously indicated, the amines can
be substituted with other groups ; thus, the R', R
2 and R
3 variables, whether taken singly or together, can contain one or more substituents
thereon. The nature of such substituents is generally not of significant importance
and any substituent group can be present that does not exert a pronounced deterrent
effect on the ultraviolet crosslinking reaction.
[0023] Exemplary suitable organic amines are methylamine, dimethylamine, triethylamine,
isopropylamine, triisopropylamine, tributylamine, t-butylamine, 2-methylbutylamine,
N-methyl-N-butylamine, di-2-methylbutylamine, tri-2-ethylhexylamine, dodecylamine,
tri-2-chloroethylamine, di-2-bromoethylamine, metha- nolamine, triethanolamine, methyldiethanolamine,
propanolamine, triisopropanolamine, butylethanolamine, dihexanolamine, 2-methoxyethylamine,
2-hydroxyethyidiisopropylamine, allylamine, cyclohexylamine, trimethylcyclohexylamine,
bis-methylcyclopentylamine, tricyclohexadienylamine, N-methyl-N-cyclohexylamine, N-2-ethylhexyl-N-cyclohexylamine,
diphenylamine, methylphenylamine, trixylylamine, tribenzylamine, triphenethylamine,
benzyldimethylamine, N-methylethylenimine, N-cyclohexylethyleni- mine, piperidine,
N-ethylpiperidine, 1,2,3,4-tetrahydropyridine, 2-, 3- and 4-picoline, morpholine,
N-methyl morpholine, N-2-hydroxyethylmorpholine, piperazine, N,N" dimethylpiperazine
and 2,2-dimethyl-1,3-bis [3(N-morpholinylpropionyloxy]-propane. The preferred organic
amines are the tertiary amines, with the alkanol amines being most preferred.
[0024] Thus is seen that the constitution of photopolymerizable compositions which can be
used in the practice of the invention is widely variable. However, the compounds enumerated
above are purely illustrative. Materials subject to polymerization by actinic radiation
as well as permissable variations and substitutions of equivalent components within
particular types of compositions are well known to those skilled in the art.
[0025] The photoinitiators of the invention can be utilized in amounts ranging from 0.01
to 30 percent by weight based on the photopolymerizable composition. However, preferable
amounts of the compounds are between 1.0 and 10.0 weight percent.
[0026] The process can be carried out by mixing a quantity of a photoinitiating compound
of the invention with a photopolymerizable composition and exposing the resultant
mixture to actinic radiation. Alternatively, a one-component system comprising the
photopolymerizable composition, the photoinitiator of the invention and, if desired,
pigmentation, can be stored in the dark for a prolonged period of time prior to use
without fear of gelation.
[0027] A preferred manner of practicing the invention is by the use of photopolymerizable
molding and coating compositions which consist of mixtures of unsaturated polymeric
compounds and monomeric compounds copolymerizable therewith. The polymeric compounds
can be conventional polyesters prepared from unsaturated polycarboxylic acids such
as maleic acid, fumaric acid, glutaconic acid, itaconic acid, citraconic acid and
mesaconic acid, and polyhydric alcohols such as ethylene glycol, diethylene glycol,
glycerol, propylene glycol, 1,2-butanediol, 1,4-butanediol, pentaerythritol and trimethylolpropane.
The carboxylic acid content can also contain saturated components. The inclusion of
a monobasic fatty acid content, either as such or in the form of a triglyceride or
oil, in the photopolymerizable polyester composition to comprise an alkyd resin is
also acceptable. These resins can, in turn, be modified by silicones, epoxides or
isocyanates, by known techniques.
[0028] The compositions of the instant invention after being prepared in the ratios as set
out above can be applied to the material to be coated by conventional means, including
brushing, spraying, dipping, and roll coating techniques, and may, if desired, be
dried under ambient or elevated conditions to provide coatings on the substrate. The
substrate can be of any composition, including but not limited to plastic, fiber,
ceramic, glass, etc.
[0029] After the composition is applied to the desired substrate, it is exposed to light
radiation having wave lengths of above about 2 000 Angstrom units, preferably from
about 2 000 up to about 8 000 Angstroms and most preferably between about 2400 Angstroms
and 5400 Angstroms. Exposure should be from a source located about 2.54 to 12.70 cm
from the coating for a time sufficient to cause crosslinking of the composition.
[0030] The light radiation can be ultraviolet light generated from low, medium, and high
pressure mercury lamps. This equipement is readily available and its use is well known
to those skilled in the art. Other sources could include electron beam radiation,
plasma arc and laser beams.
[0031] While any of the compounds having the formula I can be used in the practice of this
invention, preferred are those compounds where m and n are 0 ; R is alkyl of 1 to
12 carbon atoms, alkenyl of 3 to 5 carbon atoms, alkoxysubstituted alkyl of 2 to 4
carbon atoms or aminosubstituted alkyl of 2 to 5 carbon atoms. Particularly preferred
are the p-benzoylbenzoates, i.e., compounds I where X is OR.
[0032] In the following examples, which will serve to illustrate the practice of this invention,
all parts and percentages are by weight unless otherwise specified.
Example 1
[0033] To a magnetically stirred solution of 5.0 grams (0.022 mole) of p-benzoylbenzoic
acid in benzene was added 5.0 grams (0.24 mole) of phosphorus pentachloride. After
heating under reflux all volatile components were removed on a rotary evaporator.
To the residual solid p-benzoyl benzoic acid chloride was added methanol and the mixture
was warmed briefly to cause dissolution. All volatiles were once again removed on
a rotary evaporator to provide 5.2 grams of a white solid, representing a 98 % yield
of methyl-p-benzoylbenzoate. The infrared spectrum showed carbonyl bands at 1 650
and 1 715 cm-
1 and the absence of a carboxylic acid band at 3 300-2 000 cm-
1, confirming the formation of methyl-p-benzoylbenzoate.
[0034] To a standard test solution consisting of 42 % by weight of trimethylolpropane triacrylate,
17 % by weight of ethylhexyl acrylate and 41 % by weight of ACTOMER X.80 @ Resin,
an unsaturated long chain linseed oil alkyd resin, available from Union Carbide Corporation,
was added 4.0 % by weight of methyl p-benzoylbenzoate.
[0035] Cure rates ware determined in air using as a source of actinic light a PPG Model
QC 1202 AN UV Processor manufactured by PPG Industries, Inc. The radiation source
for this apparatus consists of two high intensity medium pressure quartz mercury lamps
30.5 cm in length and each operating at a linear power density of about 200 watts
per 2.54 cm or 2 400 watts per lamp. The lamps are housed in an elliptical reflector
above a variable speed conveyor belt and each lamp provides a 5.08 cm band of high
flux actinic radiation on the conveyor. This 5.08 cm exposure area is bordered on
both sides by an additional 5.08 cm area of medium flux energy for a total radiation
area of 15.24 cm for each lamp. In the curing data presented below, cure rate of the
polymerizable composition is presented in cm-per-minute- per-lamp (cm/min/lamp). Thus,
a conveyor belt speed of 30.5 cm/min will, with a 30.5 cm exposure area for the two
lamps, provide 60 seconds of exposure or a cure rate of 15.24 cm/min/lamp. Similarly,
a belt speed of 305 cm/min will provide 6 seconds of exposure or a rate of 15.24 cm/min/lamp
while a speed of 610 cm/min will give 3 seconds exposure or a rate of 305 cm/min/lamp,
etc.
[0036] The composition had a cure rate of 610 cm/min/lamp.
Example 2
[0037] To a mechanically stirred solution of 1 000 grams (7.12 moles) of benzoyl chloride
in 6000 grams of toluene was added 1 000 grams (7.50 moles) of anhydrous aluminum
chloride over a 20-30 minutes period. The temperature of the reaction mixture rose
to near the boiling point during the addition, and heating at reflux was maintained
for three additional hours. After cooling, 1 200 milliliters of water were added,
slowly at first, followed by 1 000 milliliters of concentrated hydrochloric acid.
The organic layer was separated ; washed twice with hot water and concentrated on
a rotary evaporator. Vacuum distillation of the residual oil provided 1 300 grams
(93 % yield) of white, semi-solid methyl benzophenone ; (b.p. 180-200 °C, 10-15 mm
Hg ; m.p. 50 °C). The infrared spectrum revealed a carbonyl band at 1 665 cm-
1.
[0038] The amount of 1 300 grams (6.65 moles) of methyl benzophenone was then melted and
heated to 170-180 °C in a 2 liters two necked round bottom flask with magnetic stirring.
Chlorine gas was introduced through a gas dispersion tube immersed below the liquid
at a rate such that the characteristic greenish color of chlorine was not detectable
in the exiting stream of hydrogen chloride. After 12 hours, the hot melt was poured
into 8 liters of isopropyl alcohol. This mixture was chilled to - 5 to 0 °C and the
precipitated solid removed by suction filtration to provide 1 600 grams (81 % yield)
of 4-(trichloromethyl) benzophenone, mp 109-111 °C. A carbonyl band at 1 670 cm-
1 was noted in the infrared spectrum.
[0039] A mixture of 1 600 grams (5.35 moles) of the 4-(trichloromethyl) benzophenone, 4
000 milliliters of n-butanol and 2 400 milliliters of 19 % by weight aqueous hydrochloric
acid was mechanically stirred at the reflux temperature for three hours. Then three
liters of water was added. The upper organic layer was separated and stirred with
4 000 milliliters of 10 % aqueous sodium carbonate solution. The organic layer was
again separated and washed twice with hot water. Removal of volatile components under
reduced pressure produced 1 400 grams (93 % yield) of semi-solid, off-white n-butyl-p-benzoyl-benzoate,
m.p. 50-60 °C. Carbonyl bands in the infrared spectrum at 1 670 and 1 730 cm-
1 confirmed the structure of the product.
[0040] Varying concentrations of the n-butyl-p-benzoylbenzoate were added to samples of
the standard test solution described in Example 1 ; the cure data is presented below.
Where ranges for cure rates are indicated, several samples were tested, with purer
esters giving the faster rates.
Example 3
[0041] The amount of 4 % by weight of the n-butyl-p-benzoylbenzoate prepared in Example
2 was added to resin samples comprising 50 % by weight of EPOCYRL 8 Resin DRH-303,
a diacrylate ester of Bisphenol A epoxy resin available from Shell Chemical Company,
and 50 % by weight of 1,6-hexanediol diacrylate available from Celanese Corporation.
A cure rate ranging from 915 to 1 220 cm/min/lamp was obtained for several samples.
Comparative examples
[0042] In order to demonstrate the efficacy of the para esters of this invention, the ortho
and meta isomers of the ester of Example 2 were prepared and tested. The n-butyl-p-benzoylbenzoate
was prepared by the acid-catalyzed esterification of o-benzoyl benzoic acid. The n-butyl-m-benzoylbenzoate
was prepared following the procedure and employing the ingredients described in Example
2 but substituting m-toluyl chloride for benzoyl chloride and benzene for toluene.
The cure data for 4 % by weight loading is presented below.
Example 4
[0043] Following the procedure of Example 1, but employing 4-methylpentanol instead of methanol,
the ester (4-methyl pentyl)-p-benzoylbenzoate was prepared. The structure was confirmed
by the presence of carbonyl bands at 1 670 and 1 730 cm-
1 in the infrared spectrum. When this ester was added at a level of 4 % by weight to
the test solution of Example 1, a cure rate of 457.5 cm/min/lamp was obtained.
Example 5
[0044] A solution of 5.0 g (0.020 mole) of p-benzoylbenzoic acid chloride made as described
in Example 1, in 75 ml of pyridine was magnetically stirred at ambient temperature
and treated at once with excess n-pentanol (5-10 milliliters). After 30 minutes, cold
dilute hydrochloric acid and ether was added. The organic layer was separated, washed
with dilute hydrochloric acid until the washing was acidic to litmus paper and dried
over anhydrous magnesium sulfate. Gravity filtration and concentration on a rotary
evaporator produced a greenish-yellow colored oil. The excess alcohol was removed
under vacuum with warming to afford an essentially quantitative yield of n-pentyl-p-benzoyl
benzoate showing carbonyl absorption bands in the infrared spectrum at 1 725 and 1
670 cm-
1. A cure rate of 610 cm/min/lamp was obtained at a 4 % by weight loading in the test
solution of Example 1.
[0045] In order to demonstrate the dark-storage stability of this compound, 4 % by weight
was added to another sample of the test solution. A glass jar was filled to greater
than 90 % by volume with the composition, which was then stored in the dark at 65
°C. The composition had not gelled when inspected after 3 months storage.
Example 6
[0046] n-Octyl-p-benzoylbenzoate was prepared by reacting p-benzoylbenzoic acid chloride
with n-octanol. The presence of carbonyl bands at 1 725 and 1 670 cm-
1 in the infrared spectrum confirmed that the product had been obtained. The test solution
of Example 1 was employed and the ester was added at a level of 4 % by weight ; a
cure rate of 533.8 cm/min/lamp was obtained.
Example 7
[0047] Tridecyl-p-benzoylbenzoate was prepared from para benzoylbenzoic acid chloride and
tridecanol. The infrared spectrum revealed carbonyl bands at 1 725 and 1 670 cm-
1. A cure rate of 457.5/min/lamp was obtained at a 4 % by weight loading in the test
solution of Example 1.
Example 8
[0048] (2-Ethoxyethyl)-p-benzoylbenzoate was prepared from para-benzoyl benzoic acid chloride
and 2- ethoxyethanol. The structure of the product was confirmed by the presence of
carbonyl bands in the infrared spectrum at 1 670 and 1 730 cm-
1. When added at 4 % by weight loading to the solution described in Example 1, a cure
rate of 457.5 cm/min/lamp was obtained. A sample in the same test solution was stable
after three months storage following the procedure described in Example 5.
Example 9
[0049] (2-Dimethylaminoethyl)-p-benzoylbenzoate was prepared from para-benzoylbenzoic acid
chloride and 2-dimethylaminoethanol. The structure of the product was confirmed by
the presence of carbonyl absorption bands in the infrared spectrum at 1 670 and 1
725 cm-
1. When added at 4 % by weight loading to the test solution described in Example 3,
a cure rate of 1 220 cm/min/lamp was observed.
Example 10
[0050] 3-(Dimethylaminopropyl)-p-benzoylbenzoate was prepared from para-benzoylbenzoic acid
chloride and 3-dimethylaminopropanol. The structure of the product was confirmed by
the presence of carbonyl bands in the infrared spectrum at 1 670 and 1 730 cm-
1. At a 4 % by wight loading, this ester resulted in a cure rate of 457.5 cm/min/lamp
in the test solution of Example 1 and a cure rate of 1 525 cm/min/lamp in the test
solution of Example 3.
Example 11
[0051] A mixture of 10.0 grams (0.044 mole) of p-benzoylbenzoic acid, 100 milliliters of
n-propanol and 0.25 milliliters of concentrated sulfuric acid was stirred under reflux
for 5 hours. Aqueous sodium bicarbonate solution was then added. The organic layer
was separated, dried over anhydrous magnesium sulfate and filtered. Volatiles were
removed under vacuum with warming to provide 9.0 grams (76.3 % yield) of n-propyl-p-benzoylbenzoate.
The infrared spectrum revealed carbonyl absorption bands at 1 670 and 1 730 c
m-1.
[0052] At a loading of 4 % by weight in the test solution of Example 3, this ester exhibited
a cure rate of 762.5 cm/min/lamp.
Example 12
[0053] Following the procedure of Example 2, iso-butyl-p-benzoylbenzoate was prepared from
20 grams of p-benzoyl benzotrichloride, 50 milliliters of iso-butanol and 30 milliliters
of 19 per cent by weight aqueous hydrochloric acid. When added at a loading of 4 %
by weight to the test solution described in Example 3, a cure rate of 915-1 067.5
cm/min/lamp was observed for several samples.
Example 13
[0054] Following the procedure of Example 6, (4-pentenyl)-p-benzoylbenzoate was prepared
from p-benzoylbenzoic acid chloride and 4-pentenol. The structure of the product was
confirmed by the presence of carbonyl bands in the infrared spectrum at 1 670 and
1 730 cm-
1. At a loading of 4 % by weight, a cure rate of 457.5 cm/min/lamp was obtained in
the test solution described in Example 1.
Example 14
[0055] N,N-diethyl-p-benzoyl benzamide was prepared by reacting p-benzoylbenzoic acid chloride
with diethylamine. At a 4 % by weight loading in the test solution described in Example
1 a cure rate of 228.8-305 cm/min/lamp was observed for several samples.
Example 15
[0056] N-iso-butylamine was reacted with p-benzoylbenzoic acid chloride to provide N-iso-butyl-p-benzoyl
benzoic benzamide. At a 4 % by weight loading in the test solution described in Example
1, a cure rate of 228.8-305 cm/min/lamp was observed for several samples.
Example 16
[0057] N,N-di-n-butyl-p-benzoyl benzamide was prepared from p-benzoylbenzoic acid chloride
and di-n-butylamine. A cure rate of 305 cm/min/lamp was observed at a 4 % by weight
loading in the test solution described in Example 1. A rate of 152.5 cm/min/lamp was
observed at the same loading in the test solution described in Example 3.