Production of radiation curable partial esters of anhydride-containing copolymers

Radiation-curable low molecular weight partial ester copolymer compositions comprising products of a terminally ethylenically unsaturated compound and a maleic anhydride characterized by having free-anhydride functionality are provided. The partial esters are produced by esterification of certain copolymers under anhydrous conditions with a hydroxyalkyl acrylyl compound, or an admixture thereof with a monohydric alcohol. The compositions of the invention are useful as radiation cross-linkable diluents for radiation-hardenable compositions, particularly in improving adhesion promotion and/or dispersive capabilities of binder resins.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the production of certain copolymer compositions 
containing free anhydride functionality. These copolymers are low 
molecular weight esterification products of a terminally ethylenically 
unsaturated compound and a polymerizable maleic anhydride and are 
polymerizable or curable by radiation such as ultraviolet, electron beam, 
and the like. The cured products of these novel compositions provide 
adhesion to a variety of substrates when present in conventional binder or 
coating systems and promote dispersion of inorganic compounds such as 
metal oxides, pigments and the like. Hence, the cured products based on 
the novel partial esters of the present invention are useful in 
radiation-curable inks, coatings and adhesives for a variety of 
substrates, such as paper, plastics, glass, metals and the like. 
2. Description of the Prior Art 
Irradiation as a method of curing free radical polymerizable compositions 
has a number of advantages over heat or ambient temperature curing, 
including: rapid cure at ambient temperatures; elimination of solvents 
together with the environmental problems associated therewith and the cost 
of their recovery; elimination of direct use of fossil fuels for curing 
and their polluting effects; capability of coating heat-sensitive 
substrates; obtainment of excellent physical and electrical properties of 
resulting products; and achievement of various cost savings by use of 
automation and high speed operation and high production. However, 
radiation curing at times introduces its own difficulties, such as in 
connection with formulation of compositions having varying degrees of 
viscosity and flow to permit commercially acceptable radiation curing, use 
of toxic components, and inhibition of curing by air contact. These 
difficulties may be substantially overcome by selective formulation of the 
radiation curable compositions, and hence, the selection of components of 
radiation curable compositions becomes critical if the advantages of 
radiation curing are to be realized and desirable useful commercial 
products obtained. 
Radiation-hardenable coating compositions are well known in the art. 
Monomers typically used heretofore for such purposes include acrylic and 
methacrylic acid esters of various diols and triols, such as 
1,6-hexanediol, diethylene glycol, 1,4-butanediol, trimethylolpropane, 
pentaerythritol or glycerol, as well as alkoxylated, such as ethoxylated 
and propoxylated derivatives thereof. Representative of patents directed 
to radiation polymerizable compositions include U.S. Pats. Nos. 3,594,410 
and 3,380,831 concerned with printing and thermal transfer reproduction 
elements, as well as U.S. Pats. Nos. 3,912,670; 4,025,548; 4,183,796; 
4,243,500; 4,360,540; and 4,404,075, all of which are directed to coatings 
and adhesives. None of these patents disclose the type of monomers upon 
which the present invention is predicated. 
Half esters of styrene maleic acid anhydride copolymers have previously 
been described in U.S. Pats. Nos. 3,536,461 and 3,342,787 for applications 
other than radiation curing. Also, electro-coating compositions containing 
styrene-maleic anhydride copolymers derived from low molecular weight 
copolymers of styrene and maleic anhydride are disclosed in U.S. Pats. 
Nos. 3,862,067 and 3,884,856. In addition, esters of such copolymers with 
unsaturated alcohols are disclosed in U.S. Pat. Nos. 3,825,430, as well as 
4,401,793 concerned with production of actinic-light polymerizable esters 
and as reative thickners in anaerobic compositions, respectively, prepared 
by reacting an anhydride-containing polymer with an excess of 
hydroxyalkylacrylate or methacrylate; the esters of these patent 
disclosures are characterized as being free of unreacted anhydride groups. 
French Patent Publication No. 2,253,772 is concerned with production of 
styrene-maleic anhydride polymers which have been esterified by an 
unsaturated alcohol or by a polyol partially esterified with an 
unsaturated aliphatic acid so that it contains free hydroxyl groups. 
Finally, U.S. Pat. No. 4,293,636 relates to photopolymerizable 
compositions useful for processing printing circuit boards comprising a 
polyester, a half-esterified hydroxyalkylacrylate of a polybasic acid, 
vinyl monomer and initiator. 
SUMMARY OF THE INVENTION 
It has now been found that a certain novel class of low molecular weight 
partial esters of anhydride-containing copolymers are capable of providing 
nonaqueous radiation curable compositions without employment of an inert 
organic solvent component. Hence, such compositions eliminate or minimize 
several substantial problems of conventional curing, namely pollution 
and/or toxicity due to solvent, while simultaneously lowering process 
costs as a result of operation without solvent. 
The novel compositions of the invention are esterification products or a 
terminally ethylenically unsaturated compound and an anhydrous 
polymerizable anhydride, and are polymerizable and/or curable by radiation 
such as ultraviolet, electron beam and the like. Such compositions which 
are curable by radiation provide products which promote adhesion to a 
variety of substrates, including glass, plastic, paper and metal. In 
addition, these novel compositions curable by radiation provide products 
which promote increase in viscosity of the medium it is made a part of. 
The novel compositions of the invention are characteristically soluble in 
alkali, but, upon curing, with radiation, provide cured products which are 
insoluble in alkali. The compositions of the invention , upon radiation 
curing, yield novel polymers of up to about 100,000 molecular weight which 
are useful as pour point depressants, lubricants and surfactants. 
Accordingly, one aspect of the invention is to provide radiation-hardenable 
partial esters of free-anhydride containing copolymers which exhibit the 
aforementioned physical and chemical properties. A further object of the 
present invention is to provide a new and improved process for the 
preparation of such partial esters. A still further object of the present 
invention is to provide radiationhardenable compositions containing 
radiation curable partial esters of the present invention, which exhibit 
improved adhesion promotion in connection with the production of useful 
products such as adhesives, fillers, coatings, as well as resulting cured 
products and articles. 
DETAILED DESCRIPTION OF THE INVENTION 
The novel radiation curable compositions of the invention are partial 
esters of a hydroxyalkyl acrylyl compound, or an admixture of such acrylyl 
compound and an aliphatic or an aralkyl monohydric alcohol, and a low 
molecular weight free-anhydride-containing copolymer of a terminally 
ethylenically unsaturated compound and a polymerizable maleic anhydride. 
The radiation curable partial ester copolymer free anhydride-containing 
compositions of the invention, in general, correspond to the formula: 
##STR1## 
wherein: 
R.sub.1 and R.sub.2 are selected from the group consisting essentially of 
hydrogen, alkyl containing of from 1 to 20 carbon atoms, aryl containing 
of from 6 to 10 carbon atoms, alkaryl containing of from 7 to 14 carbon 
atoms, cycloalkyl containing of from 4 to 12, preferably 4 to 6 carbon 
atoms, and halogen such as chlorine, fluorine or bromine. R.sub.1 and 
R.sub.2 may be the same or different and preferably are each independently 
hydrogen, methyl, phenyl, benzyl, or cycloalkyl of 4 to 6 carbon atoms. 
The radicals R.sub.3, R.sub.4 and R.sub.5 are the same or different 
radicals and are selected from the group consisting of hydrogen and alkyl 
of from 1 to 5 carbon atoms, and preferably are each independently 
hydrogen and/or methyl. 
The radical R.sub.6 is the same or different radical selected from the 
group consisting of alkyl, aralkyl, and alkyl substituted aralkyl radicals 
containing of from 1 to 20 carbon atoms, and oxyalkylated derivatives of 
such radicals containing of from 2 to 4 carbon atoms in each oxyalkylene 
group, which group may be of 1 to 20 repeating units, preferably 1 to 6 
repeating units; and the radical A is a linear or branched divalent 
alkylene of from 1 to 20 carbon atoms or an oxyalkylated derivative 
thereof as described in connection with R.sub.6. 
Subscripts x, y, z and p are each whole numbers such that the sum of x, y, 
z, and p may range from 3 to about 20, x, p, and y are each equal to or 
greater than 1, and z may be 0; preferably, x is equal to 3 to 20, as well 
as to the sum of y, z and p. 
In general, the free anhydride-containing copolymer partial ester 
compositions of the invention may be liquids or free flowing solids, 
depending upon their molecular weight, and are characterized by having a 
number average molecular weight of between about 1,000 and 20,000, 
preferably between about 2,000 and 4,000, an acid number of at least about 
50, preferably between about 100 and 300, an acrylate equivalent per gram 
value of at least 0.1, preferably of between about 1 and 2, and a glass 
transition temperature of at least about 40.degree. C. and preferably 
between about 50.degree. C. and 100.degree. C. 
In forming the partial esters of the invention, about 0.1 to 49.9%, 
preferably about 30 to 45%, of the number of potential carboxyl groups 
present as acid anhydride groups in the anhydride-containing copolymer 
reactant are reacted with the hydroxyalkyl acrylyl compound, or admixture 
thereof with an aliphatic or an aralkyl alcohol. It is critical, in 
accordance with the invention, that anhydrous copolymer be employed in the 
esterification reaction and that anydrous conditions be maintained. To 
attain this end, the esterification reaction is generally carried out in 
the presence of a solvent of particular attributes to preclude hydrolysis 
of the anhydride groups. Solvents employable in the esterification 
reaction are capable of forming an azeotrope with water while being 
substantially immiscible with water; have a boiling point ranging from 
between about 100.degree. C. and 150.degree. C., preferably between about 
100.degree. C. and 120.degree. C., at ambient pressure; readily dissolve 
the copolymer, at least at the boiling point of the solvent; and are inert 
towards reaction with anhydride and mild base, if employed as catalyst. 
Solvents meeting such attributes are well known in the art, illustrative 
examples thereof being the cyclic or acyclic dialkyl or arylalkyl ketones 
such as cyclopentanone, 3-pentene-2-one, 2-pentanone, 3-pentanone, methyl 
isobutyl ketone and the like; cyclic or acylic dialkyl or aralkyl ethers, 
such as 1,4-dioxane, 2-chlorethyl vinyl ether, and the like; halogenated 
alkanes, such as 1,1,2-trichloroethane, chlorobenzene, perchloroethylene, 
and the like; nitroalkanes such as nitroethane, nitropropane, and the 
like; and organic esters such as propyl acetate, ethyl carbonate and the 
like. 
The anhydride-containing copolymer employed in preparing the partial ester 
copolymer compositions of the invention are obtained by any conventional 
polymerization technique, such as bulk, emulsion, suspension, or solution 
polymerization. From about 0.5 to about 50 mole %, preferably about 2 to 
20 mole %, of an anhydride monomer such as maleic anhydride, or lower 
alkyl substituted derivatives thereof, containing of from 1 to 5 carbon 
atoms and mixtures thereof, may be reacted with from about 50 to 99.5 mole 
%, preferably, from about 70 to about 98 mole %, of at least one 
ethylenically unsaturated monomer having the formula CH.sub.2 
.dbd.C(R.sub.1)(R.sub.2), wherein R.sub.1 and R.sub.2 are as above 
indicated. Illustrative ethylenically unsaturated monomer suitable for 
reaction with the anhydride monomer include ethylene, propylene, 1-octene, 
styrene, .alpha.- methylstyrene, p-tertiary butyl styrene, 
vinylcyclohexane, and vinyl chloride. 
Especially preferred reactants for preparation of the aforementioned 
free-anhydride containing copolymers used in the invention are 
styrene/maleic anhydride copolymers having a mole ratio of styrene to 
maleic anhydride of about 1:1 to 4:1, preferably 1:1 to 2:1. Such 
copolymers have a number average molecular weight of between about 500 and 
4,000 and preferably from about 1,000 to 3,000, the most preferred range 
being between about 1,500 and 2,500. These copolymers are commercially 
available under the tradename SMA.RTM. resins from ARCO Chemical Company, 
Division of Atlantic Richfield Company. It is critical, in accordance with 
the invention, that an anhydrous copolymer reactant be employed. Such 
reactant may be made anhydrous, i.e. any carboxyl groups present as a 
result of hydrolysis of original anhydride groups present in the 
copolymer, may be reconstituted to the anhydride state, in conventional 
manner by removing the water from the copolymer by azeotroping the 
copolymer with any convenient solvent that readily dissolves the resin. 
Alternatively, organic solvents which are immiscible in water, 
illustratively ketones, such as methyl isobutyl ketone, may be employed, 
as above indicated. 
As the hydroxyalkyl acrylyl compound employed for esterification of the 
free-anhydride containing copolymer, there may be employed a hydroxyalkyl 
acrylate or a hydroxyalkyl methacrylate, as well as oxyalkylene 
derivatives thereof containing of from 2 to 4 carbon atoms in each 
alkylene oxide unit (which may be of 1 to 20 repeating units), which 
compound corresponds to the formula: 
##STR2## 
wherein the radicals R.sub.5 and A are as indicated hereinabove. The 
hydroxyalkyl acrylyl compounds are well known in the art and may be 
illustrated by hydroxyethyl acrylate, hydroxyethyl methacrylate, 
hydroxypropyl acrylate, hydroxybutyl methacrylate, tetrapropylene glycol 
monoacrylate, tetrapropylene glycol monomethacrylate and the like. 
Alternatively, an admixture of the aforedescribed acrylyl compound and an 
aliphatic or an arylalkyl monohydric alcohol, or oxyalkylated derivative 
of such aliphatic or arylalkyl monohydric alcohol containing of from 2 to 
4 carbon atoms in each oxyalkylene group which group may be of 1 to 20 
repeating units, preferably 1 to 6 repeating units, may be employed in the 
esterification of the copolymer Typical illustrative monohydric alcohols 
employable for such purpose include alkanols such as methanol, ethanol, 
propanol, cyclohexyl alcohol, benzyl alcohol, alpha-phenethyl alcohol, 
.beta.-phenethyl alcohol, nonylbenzyl alcohol, as well as oxyalkylene 
derivatives of such alcohols wherein at least one 1,2-alkylene oxide, such 
as ethylene oxide, 1,2-propylene oxide, and 1,2-butylene oxide has been 
condensed therewith. 
Although the anhydride-containing copolymer may be first reacted with the 
hydroxyalkyl acrylate and subsequently with the monohydric alcohol, or 
alternatively, first reacted with the monohydric alcohol and subsequently 
reacted with the hydroxyalkyl acrylate, preferred practice of the 
invention resides in the simultaneous reaction of admixture of the 
hydroxyalkyl acrylate and monohydric alcohol, thereby forming the desired 
partial ester of the anhydride-containing copolymer of the invention. When 
an admixture of the hydroxyalkyl acrylyl compound and monohydric alcohol 
is employed to esterify the free anhydride-containing copolymer, the molar 
ratio of monohydric alcohol to hydroxyalkyl acrylyl compound will 
generally range from between about 1:10 to 10:1, and preferably from 
between about 1:1 and 1:5. 
The esterification reaction is carried out at the reflux temperatures of 
the reaction admixture, generally at temperatures from of about 50.degree. 
C. to 150.degree. C. and preferably from about 95.degree. C. to about 
120.degree. C. Although a catalyst need not be employed, the 
esterification reaction is normally effected in the presence of suitable 
catalyst, such as an alkali metal alkanoate, illustratively, sodium 
acetate, potassium propionate, and lithium acetate. 
To prevent radical polymerization of the resultant partial ester, there may 
also be included in the esterification reaction a radical-polymerization 
inhibitor present in amount of about 0.001 to 0.05 wt %, based on the 
weight of the partial ester. Illustrative inhibitors employable for such 
purpose include phenols exhibiting steric hindrance such as hydroquinone, 
hydroquinone monomethyl ether, 2,6-ditertiary butyl p-cresol and the like. 
The radiation-hardenable compositions of the present invention may be cured 
by means of high-energy radiation, such as electron beam, UV light, gamma 
rays, etc., but preferably by electron beam radiation. 
The radiation-hardenable compositions containing the free 
anhydride-containing copolymer partial ester of the present invention 
comprise a binder or diluent (oligomer) together with said partial ester. 
The reactive diluent component of the radiation-hardenable composition 
comprises one or more free radical polymerizable, radiation curable, 
substantially nonvolatile, liquid monomers or oligomers of up to about 
2000 molecular weight selected from monoethylenically unsaturated 
materials, polyethlenically unsaturated materials and mixtures thereof. 
The presence of amounts of polyethylenically unsaturated materials greater 
than about 5%, by weight, may introduce a degree of crosslinking in the 
radiation cured products which may render the products too rigid and 
brittle for some end uses of the present invention. However, in other 
applications thermosetting properties are desirable for chemical and stain 
resistance, higher Tg, heat and degradation resistance, and other 
properties in coatings, pottants, solder resists, sealants, fiber binders, 
and others. In such cases a polyunsaturated material may comprise a major 
proportion of the reaction diluent or all of the diluent. For applications 
in which crystallinity must be minimized, the more suitable reactive 
diluents thus primarily comprise monoethylenically unsaturated liquids 
which are radiation polymerizable. Representative types are vinyl monomers 
such as the lower alkyl esters of acrylic or methacrylic acid including 
methyl methacrylate, ethyl acrylate, 2-ethylhexyl acrylate, butyl acrylate 
and isobutyl methacrylate; vinyl esters such as vinyl acetate and vinyl 
propionate; vinyl halides such as vinyl chloride and vinylidene chloride; 
and particularly high solvency monomers such as 2,2-ethoxyethoxyethyl 
acrylate, tetrahydrofurfuryl acrylate, n-laurylacrylate, 
2-phenoxyethylacrylate, glycidyl acrylate, glycidyl methacrylate, isodecyl 
acrylate, isoctyl acrylate, and the like. Other monoethylenically 
unsaturated reactive diluents include vinyl aromatics such as styrene, 
alphamethylstyrene, vinyl toluene, indene and p-tert butyl styrene; 
ethylenically unsaturated acids such as fumaric acid, maleic anhydride and 
the esters thereof; and nitrogen containing monomers such as 
acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, 
N,N-dimethacrylamide, N-vinylpyrrolidine, N-vinylcaprolactam, and the 
like. 
The polyethylenically unsaturated reactive diluents include polyol 
polyacrylates and polymethacrylates, such as alkane (C.sub.2 -C.sub.16) 
diol diacrylates, aliphatic (C.sub.2 -C.sub.16) polyacrylates, alkoxylated 
aliphatic polyacrylates such as described in U.S. Pat. No. 4,382,135, 
polyether glycol diacrylates and the like. Typical of the foregoing are 
1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,3-butylene 
glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol 200 
diacrylate and tetraethylene glycol diacrylate. Other polyunsaturated 
reactive diluents are allyl acrylates such allylmethacrylate and 
diallylmethacrylate; acrylated epoxies, aminoplast acrylates and 
unsaturated polyesters; trimethylol propane based polyacrylates such as 
trimethylolpropane triacrylate; the pentaerythritol-based polyacrylates or 
polymethacrylates described in U.S. Pat. No. 4,399,192; acrylic oligomers; 
acrylated polymer or oil such as acrylated epoxidized drying-type oils, 
acrylated bisphenol A/epoxy resins, ethoxylated bisphenol A diacrylate, 
acrylated urethane prepolymers (also know as "acrylated polyurethanes"), 
polyethers, silicones, and the like. 
The reactive diluents are conventionally sold with a free radical 
polymerization inhibitor content ranging from about 25 to 2000 ppm. Of 
course, if the reactive diluents are produced at the site of radiation 
curing, little or no inhibitor need be present in the diluents. 
The foregoing and other reactive diluents (and inhibitors if used) are 
widely known and are described in the patent and other literature, such as 
component (1) of U.S. Pat. No. 3,368,900, component (2) of U.S. Pats. Nos. 
3,380,831 and 3,594,410, the polymerizable vehicles disclosed in U.S. 
Pats. Nos. 4,163,809 and 4,481,258, and the acrylated polymer of oils, 
acrylic oligomers and other radiation curable component (b) compounds 
disclosed in U.S. Pat. Nos. 4,360,540. All of the aforementioned patents, 
descriptive of reactive diluents useful in the present invention, are 
incorporated herein by reference. 
In addition to reactivity and desired degree of crosslinkability, the 
reactive diluents will be selected on the basis of their solvency for the 
free-anhydride containing copolymer component and their contribution to 
the viscosity of the resulting solutions. Compositions ranging from 
sprayable to extrudable character can thus be prepared. Generally, the 
less polar the reactive diluent the greater the solvency for said 
copolymer. Solvency and viscosity can be determined conveniently by 
preparing mixtures over a range of concentrations, noting the clarity and 
compatibilities, and measuring the viscosities. In those cases where 
solvency in a single diluent is insufficient, one or more other diluents 
may be added to optimize compatibility. The higher the molecular weight of 
the copolymer, the less soluble the copolymer will be in some of the 
reactive diluents. Accordingly, molecular weight of copolymer must be 
balanced with the ease with which solutions can be formed and 
acceptability of the resulting viscosities and properties relative to the 
end uses of the compositions. If the intended end use is a coating 
composition, for example, lower copolymer molecular weight, e.g., not over 
about 30,000, may be required in order to obtain good solvency and low 
viscosity in a given reactive diluent or mixture of diluents. The 
formulator of radiation curable compositions is well area of all of the 
foregoing and other considerations and can make appropriate selections of 
components of the compositions and proportions by routine experimentation 
and judgment in order to obtain a desired balance of properties. 
An inert solvent may also be added to the curable compositions to provide 
better flow or wetting and extremely thin films, e.g., less than 0.2 mils. 
The solvents may be flashed off before irradiation or left in the 
composition during the cure. Representative inert solvents are ketones 
such as methylethyl ketone, haloalkanes such as dichloromethane and other 
industrial solvents. Such solvents containing compositions have been found 
useful for imparting improved abrasion resistance to film substrates such 
as acetates, polycarbonate and others. 
Depending upon the radiation source and wavelength used in curing the 
radiation-hardenable compositions, the compositions may also contain a 
radiation responsive free radical initiator. If the radiation source is 
high energy, such as electron beam, little or no initiator may be 
required. If the radiation is lower energy, e.g., ultraviolet light, if 
the polymerizable composition is other than in the form of a thin film, 
e.g., a coating, molding or extrudate, or if the composition contains 
components (e.g., radiation absorbers, inhibitors) which interfere with or 
block the irradiation, an initiator normally will be used. The amount of 
initiator, when used, and the irradiation time will be dependent on the 
type and amounts of radiation curable components in the composition. For 
example, if the composition contains highly reactive diluents, the quantum 
and/or time of irradiation may be less. Generally, the sources of 
irradiation may be electron beams, gamma radiation emitters, carbon arcs, 
mercury vapor arcs, ultra violet light sources such as phosphors, argon 
glow lamps and photographic flood lamps; accelerators including 
Vandergraaf and Betatron linear accelerators, and the like including 
combinations thereof. High energy irradiation, such as electron beams, is 
preferred, with or without an initiator, when the curable composition is 
in a form other than thin film. 
Suitable initiators include any radiation responsive free-radical 
generating compound known in the art for such purpose, such as the UV 
responsive photoinitiators 2,2-dimethoxy-2-phenyl acetophenone, 
2-hydroxy-2-methyl-1-phenyl propan-1-one, benzoin, benzoin methyl ether, 
diphenyldisulfide, dibenzyldisulfide, benzil, benzophenone, xanthane, and 
various other acetophenones. Accelerators such as tertiary amines may also 
be added. If a higher degree of cross-linking is desired, peroxide or azo 
initiators may also be used, such as benzoyl peroxide, in conjunction with 
the free radical initiators. The foregoing and other aspects of radiation 
curing of polymerizable compositions are wellknown and are non-critical to 
practice of the invention. Further details may be found in technical 
articles on the subject such as "Radiation Curing" in the Encyclopedia of 
Chemical Technoloy, Kirk-Othmer, 3rd Edition, Volume 19, pages 607-624, 
incorporated herein by reference. 
The radiation curable compositions of the invention provide useful products 
without inclusion of additives conventionally employed with such 
compositions. For example, a mixture comprised of about 6 parts by weight, 
of free-anhydride containing copolymer, about 8 parts of a reactive 
diluent such as trimethylolpropane triacrylate and about 0.64 parts of a 
photoinitiator can be applied to a suitable substrate and cured by 
exposure to UV radiation to form a clear, flexible, strongly adherent, 
tack-free film, thus demonstrating efficacy as an adhesive coating and a 
film forming material. Nevertheless, additives will improve and/or modify 
the useful properties of the compositions upon radiation curing to an 
extent which is surprising and unexpected. For reasons not fully 
understood, the presence of additives in the radiation curable 
compositions prior to curing as opposed to blending additives into a cured 
polymeric composition, further enhances the properties of the composition 
beyond what might have been anticipated based upon post blending 
experience. Possibly, the additives in some manner interact with the free 
anhydride-containing copolymer and/or the reactive diluent, whereas they 
do not appear to so interact if blended into a radiation cured mixture of 
copolymer and diluent. 
Generally, the additives are non-reactive with the copolymer, i.e., will 
not copolymerize therewith, and should disperse well in the solution of 
copolymer in reactive diluent. Preferably, the additives should dissolve 
in such solution and should not interfere in the dissolving of the 
copolymer by the reactive diluent. At least 0.5% of additive based on 
total weight of composition may be used for efficacy. 
When the objective is to prepare adhesives, the radiation curable 
composition will contain at least about 5 wt.% of copolymer, and the types 
and quantities of copolymer, reactive diluent and additives are selected 
to obtain an acceptable T.sub.g in the cured product. Since many of the 
reactive diluents will have a lower T.sub.g than the copolymer, the 
T.sub.g and thermoplasticity of the cured product can largely be 
controlled by selection of reactive diluent and amounts thereof. For 
further enhancement of adhesive properties, or to modify the 
thermoplasticity provided by the copolymer, one or both of an elastomeric 
base (preferably non-crystallizable) and a tackifier may be added to the 
radiation curable mixture of copolymer in reactive diluent. Elastomeric 
materials are useful for making the cured product more impact resistant 
and to provide enhanced shear strength, elongation and modulus. Tackifiers 
are useful for more sharply delineating the liquid and solid phases of the 
cured composition, to improve adhesion or to improve bonding to different 
substrates. From about 5 to 50% by weight of either the elastomeric base 
or of tackifying resin, based on total composition, are useful. If 
mixtures of elastomer and tackifier are used, the mixtures can vary from 
about 5 to 50% of either component. 
Any elastomeric materials and tackifiers known in the art may be used. 
Among the elastomeric bases may be mentioned natural rubber and synthetic 
rubbery materials such as polyisobutylene, polyvinylisobutylether, 
neoprene, polyvinylbutyral, chlorosulfonated polyethylene, and various 
copolymers prepared from two or more of butadiene, acrylonitile, styrene, 
isoprene, and the like. Many other synthetic resins also have elastomeric 
properties and are useful as elastomeric additives, such as vinyl toluene 
resins and polyester resins. The elastomers and may be used singly or in 
admixture. 
Suitable tackifying resins include any of the essentially saturated 
thermoplastic resin polymers known in the art for their tackifying 
properties, such as rosin esters, hydrogenated esters of rosin, modified 
rosin esters, esters of polymerized rosin, esters of hydrogenated rosin, 
hydrocarbon resins, polyalphamethylstryene, alpha pyrene terpene resins, 
polyalphamethylstyrene, alpha pyrene terpene resin, vinyl 
toluene/alphamethylstyrene copolymer resins, beta-pinene terpene resins, 
polycyclic hydrocarbon resins, and the like. The hydrocarbon elastomers 
are preferred. 
When radiation cured in accordance with the invention, the foregoing 
compositions with or without elastomeric base and/or tackifier, but 
preferably with such additives, produce high quality pressure sensitive 
adhesives having excellent lap-shear and other properties. 
The copolymers when combined with low reactivity diluents such as the mono 
acrylates or methacrylates, will form, upon radiation curing, 
heat-sealable films having a melting range characteristic of polyvinyl 
aromatics, e.g., polystyrene. The films can be self-supporting or can be 
supported on any surface to which they will adhere, e.g., paper or other 
fibrous material, wood, particle board, plastic sheets of other films, and 
the like. They can also be used to bond one or more layers in 
multi-layered systems or laminates. For example, one side of a sheet of 
paper may be printed with a desired pattern and given a clear top coat, 
and the other side coated with a film-forming composition of the 
invention, the entire system then being cured by irradiation. This 
composite can then be heat-laminated onto rigid, semi-rigid or flexible 
substrates such as wood, particle board, metal or other films, with the 
films in contact with the substrate, to form a decorative surface or 
article. Cured, unsupported films can similarly be heatsealed to various 
substrates. 
Radiation curable compositions of the invention will form heat-sealable 
films so long as they remain thermoplastic upon radiation cure. To insure 
thermoplasticity, no more than 10 wt. % of the reactive diluent, based on 
total radiation curable composition, should comprise polyethylenically 
unsaturated material, and preferably no more than about 5 wt. %. It may be 
desirable in some cases to add an elastomeric material and/or a tackifier 
to the film-forming composition prior to curing. As in the case of 
adhesives, films of the compositions can be radiation cured with a variety 
of radiation sources. High energy sources, such as electron beam, will 
require no free radical initiator in the composition. Lower energy 
sources, such as UV, will require an initiator, such as a photoinitiator 
in the case of UV-curing. 
The films will be essentially tack-free, thus further enhancing their 
utility as heatsealable films. Tack-free quality is achievable in 
compositions containing tackifier and/or elastomer by careful selection of 
the type and amount of additive. 
The films are formed, bonded to various substrates or laminated using 
processing techniques and conditions well-known in the adhesives and films 
industries. 
The low-shrinkage characteristic of the radiation cured products produced 
from the polymerizable compositions of the invention makes them suitable 
as embedding compositions in various industries to the extent that 
radiation can penetrate and thereby cure the compositions. Specifically 
the compositions are useful in the electrical and electronics fields for 
the encasement of electrical and electronic circuity and parts, and as 
fillers for dental use and the production of decorative or functional 
objects such as statuary, cast parts, and the like. "Embedding" as used 
herein generically includes casting (pouring a hardenable liquid into a 
mold containing a part to be embedded and removing the mold after 
hardening), potting (same as coating except the mold remains as an 
integral part of the hardening unit), impregnating (immersion of a part so 
that the hardenable liquid fills the interstices of the part), 
encapsulating (thickly coating a part with a hardenable liquid), and 
transfer molding (transfer of hardenable liquid under pressure into a mold 
containing the part to be embedded). Since the hardenable liquid (the 
radiation curable composition of the present invention) must be radiation 
cured in a form other than a thin film, either high energy irradiation 
(such as electron beam) is necessary for curing or the composition must 
contain a fairly low concentration (about 0.1-10 wt. % on total 
formulation) of photoinitiator if UV light is used for curing. 
Viscosity of the curable compositions is also an important consideration. 
The viscosity must be sufficiently low so that the composition will flow 
completely around the part to be embedded at processing temperature and 
pressure in the case of casting, potting and transfer molding. The 
viscosity should be even lower in the case of impregnating, but higher 
viscosity (along with thixotrophy) is necessary for encapsulating to avoid 
run-off during cure. 
Usually the radiation curable composition for such applications will 
contain sufficient polyethylenically unsaturated reactive diluent for 
substantial crosslinking during the cure; however, useful products which 
remain totally thermoplastic but hard are also producible. 
As fillers the radiation curable compositions can be used in polymer 
concrete, adhesives, sealants and bonding agents of all types; and can be 
admixed with silicate or fiberglass fillers, pigments, adhesion promoters, 
and flow control agents and a variety of other materials commonly employed 
in the manufacture of decorative articles, construction materials such as 
glazing, fiberboard and siding, embedded electronic and electronmechanical 
assemblies, and a host of other products. 
Typically in the foregoing applications a base composition of about 10-75 
wt. % of macromonomer in reactive diluent is first prepared and to this 
composition is added any other materials for obtaining the end use 
products desired. Alternatively, the base composition can be blended into 
another composition as a filler. 
In radiation curable coatings, such as paints, lacquers and varnishes, the 
radiation curable compositions of the invention may be present as the 
major constitutent, such as replacement for the oligomer in oligomer 
coatings, or may be present as an additive for improvement of certain 
properties, such as adhesion promotion in oligomer coatings. In the former 
application the copolymer may amount to about 20-70 and the reactive 
diluent about 30-80 wt. %, based on total composition, the balance being 
flow promoters (wetting agents), pigment, coupling agents, slip agents, 
thixotropic agents, or other modifiers conventionally present in oligomer 
coatings. In the latter application, preferred ranges are about 2-10 wt. % 
of macromonomer the balance being reactive diluents, oligomer and 
additives. The oligomer component of the coating compositions may comprise 
any of the base materials or bodying agents known for use in nonaqueous, 
radiation curable coatings. These include polyesters such as the 
polyethylene polyurethanes of U.S. Pat. No. 4,183,796, the acrylic acid 
adducts of epoxidized phenolformaldehyde adducts, acrylic acid adducts of 
the diglycidyl ether or bisphenol A, acrylic acid adducts of soybean oil, 
the monohydroxy vinyl compound-epoxy adducts of U.S. Pat. No. 4,025,548 
wherein the vinyl compound may be a vinyl, allylic, acrylic or methacrylic 
material, crosslinkable oils and oligomers such as are described in U.S. 
Pat. No. 3,912,670, and reaction products of 1-alkenes and acrylic 
derivatives such as described in U.S. Pat. No. 4,009,195. 
The coatings may be applied by any suitable means, such as spraying, 
dipping, flow coating, brushing, and the like, followed by or 
simultaneously with irradiation. 
Radiation curable compositions of the invention may also be formulated for 
extrusion coating of various substrates and articles such as wire, cables 
and coils. In these as well as in other coating applications, viscosity 
control and flow is important; consequently it may be desirable to add a 
flow control agent (also known as wetting dispersant or spreading agents) 
to the composition. Representative flow control agents particularly for 
extrusion applications, are cellulose acetate butyrate polymers, 
styrene-allyl alcohol copolymers, polyvinylbutyrals and polyvinylethers 
such as the "Gantrez" maleic anydride copolymer resins sold by GAF 
Corporation. The radiation curing conditions can be selected for the 
specific system in accordance with criteria well known in the art. In 
these applications, for example, electron beam irradiation and 
three-dimensional curing are often used, due to the greater thickness of 
material to be cured. 
The following examples will serve to illustrate the invention, but it is 
understood that these examples as well as other embodiments set forth in 
the specification are merely representative of the invention and do not 
necessarily limit the scope thereof. In the examples and throughout the 
specification and claims, all parts and percentages are by weight unless 
otherwise expressly stated.

EXAMPLE 1 
Into a reaction vessel equipped with an agitator, an air inlet tube and a 
condenser, there was charged 300 parts of anhydrous styrene-maleic 
anhydride copolymer having a number average molecular weight of about 
1,600 and an acid number of 480, 85.5 parts of 2-hydroxyethyl acrylate, 
12.7 parts of methanol, 1.2 parts of lithium acetate, 0.17 parts of 
hydroquinone, and 600 parts of methyl ethyl ketone solvent. Air was 
greatly sparged through the reaction mixture while heating at reflux and 
collecting water of esterification for a period of about 10 hours, i.e. 
until the infra-red spectrum of the reaction mixture showed no more 
reduction in the intensity of the anhydride absorption. Following the 
reflux period indicated, the reaction mixture was poured into heptane, 
thereby causing precipitation of a fine solid, and filtered to provide a 
free-flowing solid as a reaction product. Following drying, 400 parts of 
desired free-anhydride-containing copolymer product conforming to the 
formula: 
##STR3## 
was obtained, The product had an acid number of 194 and an acrylate 
equivalent of 1.84 meg. per gram. 
EXAMPLE 2 
A radiation curable free anhydride-containing copolymer was prepared while 
employing the proceduce of Example, 1, except that the following reactants 
were employed in the quantities indicated: 
Anhydrous styrene maleic anhydride copolymer as described--300 parts 
2--hydroxyethyl methacrylate--25.4 parts 
lauryl alcohol--9.7 parts 
lithium acetate--1.2 parts 
hydroquinone--0.7 parts 
methyl ethyl ketone--600 parts 
Following drying, 346 parts of the desired free-anhydride-containing 
copolymer products conforming to the formula: 
##STR4## 
was obtained. The product had an acid number of 380 and a methacrylate 
equivalent of 0.58 meq, per gram. 
EXAMPLE 3 
A radiation curable free anhydride containing copolymer was prepared while 
employing the procedure of Example 1, except that the following reactants 
were employed in the quantities indicated: 
anhydrous styrene maleic anhydride copolymer having a molecular weight of 
about 1900 and acid number of 275--828.5 parts 
4hydroxy butyl acrylate--207.4 parts 
ethylene glycol monobutyl ether--42.5 parts 
lithium acetate--1.2 parts 
hydroquinone--0.17 parts 
methyl ethyl ketone--600 parts 
Following drying, 1,080 parts of the desired free-anhydride-containing 
copolymer product conforming to the formula: 
##STR5## 
was obtained. The product had an acid number of 114 and an acrylate 
equivalent of 1.34 meq. per gram. 
In order to evaluate the free-anhydride containing copolymer compositions 
of the invention, typical radiation curable formulations containing the 
free-anydride-containing copolymer product of Example 1 (with varying 
amounts of 2-hydroxyethyl acrylate) were formulated and cured as two mil 
thick, free films, which were then tested for adhesion, pencil hardness, 
and reverse impact, in accordance with established A.S.T.M. procedures. 
The results of these evaluation are set forth in Table I below: 
TABLE I 
__________________________________________________________________________ 
TS BY WEIGHT 
FORMULATION A B C D E F G H 
__________________________________________________________________________ 
SMA Acrylate.sup.(1) 6 4 -- -- -- -- -- -- 
SMA Acrylate.sup.(2) -- -- 6 4 -- -- -- -- 
SMA Acrylate.sup.(3) -- -- -- -- 6 4 -- -- 
Urethane Acrylate.sup.(4) 
-- -- -- -- -- -- 6 4 
Carbitol Acrylate.sup.(5) 
4 2 4 2 4 2 4 2 
Trimethylolpropane Triacrylate.sup.(6) 
8 -- 8 -- 8 -- 8 -- 
Darocure .RTM. 1173 Photoinitiator.sup.(7) 
0.64 
0.4 0.64 
0.4 0.64 
0.4 0.64 
0.4 
1,6-Hexanediol Diacrylate.sup.(8) 
-- 4 -- 4 -- 4 -- 4 
FILM PREATION & PROPERTIES.sup.(13) 
Substrate .rarw.BONDERITE STEEL.fwdarw. 
Cure Speed.sup.(9) 30 .times. 1 
30 .times. 1 
30 .times. 2 
30 .times. 1 
30 .times. 1 
30 .times. 1 
30 .times. 1 
30 .times. 1 
Wet Thickness (mils) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 
Adhesion.sup.(10) - UV cure only 
5 1 5 2 5 3 0 0 
Hardness.sup.(11) (pencil) - UV 
5H 5H 5H 5H 5H 5H 5H 6H 
Reverse Impact.sup.(12) UV cure only 
0-2 6-8 0-2 4-6 0-2 2-4 18-20 
50+ 
__________________________________________________________________________ 
FOOTNOTES: 
.sup.(1) Styrenemaleic anhydride reaction product with 15% hydroxyethyl 
acrylate and 30% methanol 
.sup.(2) Styrenemaleic anhydride reaction product with 30% hydroxyethyl 
acrylate and 30% methanol 
.sup.(3) Styrenemaleic anhydride reaction product with 60% hydroxyethyl 
acrylate and 30% methanol 
.sup.(4) Aliphatic urethane acrylate ester available from the Sartomer 
Company as ChemLink .TM. 9004 oligomer 
.sup.(5) 2(2ethoxy-ethoxy)ethylacrylate available from the Sartomer 
Company as SR256 
.sup.(6) available from the Sartomer Company as SR351 
.sup.(7) available from EM Chemicals 
.sup.(8) available from Sartomer Company as SR238 
.sup.(9) using 2 .times. 300 watt/In Hg Lamps, cure speed of 30 .times. 
equals 1.7 Joules/centimeters.sup.2 
.sup.(10) ASTM D 335078 
.sup.(11) ASTM D 336374 
.sup.(12) ASTM 229474 
.sup.(13) adhesion, pencil hardness and reverse impact properties obtaine 
on cured coatings following at least 16 hours ageing or conditioning 
As is apparent from the results set forth in Table I, all of the 
radiation-hardenable compositions containing the copolymer of the 
invention resulted in the highest value in the adhesion test, in 
contradistinction to the radiation-hardenable composition containing the 
urethane acrylate which shows no adhesion capabilities. Although the 
radiation hardenable composition containing the urethane acrylate appeared 
superior in reverse impact testing, which is a measure of the flexibility 
of the coating, all of the radiation hardenable compositions tested were 
essentially equivalent in pencil hardness. 
In summary, it will be apparent to those skilled in the art that numerous 
modifications may be made in the various embodiments of the invention 
described above without departing from the spirit or scope of the 
invention. Thus, various auxillary materials may be added to the radiation 
curable compositions, such as rheology control agents (e.g. silica gel or 
other thickener filler), antioxidants, color stabilizers, dyes, pigments 
and other colorants, flattening agents, radiopaquing agents, impact 
modifiers, and the like. As coatings, adhesives and films the compositions 
can be used as paints, varnishes, lacquers, co-elastomers with other 
elastomers, sealants, binders or impregnating agents for wood, paper and 
other fibrous materials, solder resists, and as protective coatings or 
interlayers for glass, transformer coils and metals or films of all kinds. 
Moreover, the compositions before or after radiation curing can be 
topcoated with organic solvent based coatings or water-based coatings, and 
can be applied as prime coats, base coats or single coat systems. The 
compositions can also be used in printing plates, imaging materials, 
magnetic media, and in embossing materials and processes. Lastly, as 
embedding and casting materials, the compositions may be tailored to meet 
the requirements of various industries such as dentistry, the medical arts 
and electronics.