Coreactive conjugated diene polymer compositions which phase separate when cured

This invention provides a reactive conjugated diene polymer composition that forms a phase-separated adhesive, sealant, or coating. The composition comprises an epoxidized polymer of conjugated dienes, a second reactive component which is phase separated from the polymerized conjugated diene upon cure, and optionally a tackifying resin. The invention also encompasses adhesive, coating and sealant compositions made with the above composition.

FIELD OF THE INVENTION 
This invention relates to reactive conjugated diene polymer compositions 
which are cured to form crosslinked adhesives, sealants, and coatings. 
BACKGROUND OF THE INVENTION 
Curing of adhesives, sealants, and coatings based on conjugated diolefins 
and, optionally, vinyl aromatics has increased the range of service 
properties for such compositions. Chemical or radiation curing of reactive 
conjugated diene polymers to make such crosslinked compositions is known. 
This curing causes covalent crosslinking of the polymerized conjugated 
dienes which is evidenced by a high gel content of the crosslinked 
polymer. Before crosslinking, the polymers are melt and solution 
processable but after crosslinking, the gel cannot be processed as melts 
or in solution. Crosslinking therefore enhances solvent resistance and 
improves elevated temperature shear properties, toughness and cohesion. 
Compositions can therefore be applied to a substrate in a melt or from 
solution and then crosslinked to form a superior adhesive, coating or 
sealant. 
The presence of styrene blocks in the reactive conjugated diene polymers 
can result in a phase separated reactive block copolymer which can cure to 
form a phase separated adhesive, sealant, or coating. However, the styrene 
containing polymers are more difficult to process since the styrene blocks 
promote physical crosslinking of the reactive polymers prior to curing. 
Curable adhesives, sealants and coatings which are based on epoxidized 
polymers are described in U.S. Pat. No. 5,229,464, issued Jul. 20, 1993, 
(T4797X) which is incorporated by reference herein. The epoxidized 
polymers may be blended with other reactive polymers as disclosed in the 
'464 patent to provide a balance of desired properties. 
It is an object of the present invention to provide improved adhesive, 
sealant, and coating compositions which are easily processable in the melt 
or at high solids content before crosslinking but have a high gel content 
after crosslinking. Further, it is an object of this invention to provide 
an adhesive, coating or sealant composition which is based on this 
improved crosslinked block copolymer composition that achieves a unique 
balance of tack and strength properties. 
SUMMARY OF THE INVENTION 
This invention provides a conjugated diene based polymeric composition 
which cures to a phase separated adhesive, sealant, or coating. The 
composition is a coreactive blend of an epoxidized conjugated diene 
polymer which can be a linear, radial, or star polymer, and a coreacting 
polymer or diluent which forms a phase-separated crosslinked network in 
combination with the epoxidized polymer upon cure. Examples of epoxidized 
polymer formulations which result in phase separated cured adhesives, 
coatings or sealants include epoxidized conjugated diene/vinyl aromatic 
block copolymers and vernonia oil (a natural epoxy functional oil). 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention is a radiation curable composition, containing from 
20 to 70% by weight of an epoxidized polymer of a saturated or an 
unsaturated conjugated diene, from 1 to 30% by weight of a coreactant 
selected from the group consisting of epoxidized oils and epoxidized 
linear polymers that phase separate from the epoxidized star polymers upon 
cure, and from 0 to 80% by weight of a tackifying resin. 
The epoxidized polymers include conjugated diene polymers having controlled 
epoxidation such as the radial polymers as described in U.S. Pat. No. 
5,229,464, issued Jul. 20, 1993, entitled "Viscous Conjugated Diene Block 
Copolymers" (T4797X), which is incorporated herein by reference. The 
epoxidized star polymers typically have at least 4 polymeric arms per 
molecule with each arm having a peak molecular weight from 3,000 to 
18,000, preferably 3,000 to 7,000. In order to make low viscosity 
compositions, the epoxidized star polymers, which have high total 
molecular weights in comparison to uncoupled linear polymer arms, do not 
contain polymeric segments or blocks that would phase separate prior to 
formulation of the radiation curable composition. The concentration of 
di-, tri-, or tetrasubstituted olefinic epoxides (1,1-disubstituted, 
1,2-disubstituted, 1,1,2-trisubstituted and 1,1,2,2-tetrasubstituted 
olefinic epoxides) is from 0.05 to 5 milliequivalents of epoxide per gram 
of polymer (Meq/g), preferably from 0.1 to 3 Meq/g. 
Useful randomly epoxidized star polymers are described in U.S. Pat. No. 
5,247,026, issued Sep. 21, 1993, entitled "Randomly Epoxidized Small Star 
Polymers, " which is herein incorporated by reference. That patent 
describes randomly epoxidized star polymers, based on at least one 
conjugated diolefin monomer, that contained di-, tri- and/or 
tetrasubstituted olefinic epoxides. The star polymers have greater than 
four arms or branches. Each arm has a molecular weight from 1500 to 15,000 
and the concentration of di-, tri-, or tetrasubstituted olefinic epoxides 
(1,1-disubstituted, 1,2-disubstituted, 1,1,2-trisubstituted and 
1,1,2,2-tetrasubstituted olefinic epoxides) is from 0.05 to 5 
milliequivalents of epoxide per gram of polymer. In this invention, we 
prefer 0.1 to 3 Meq/g. 
Other useful block copolymers are based on at least one conjugated diolefin 
monomer, contain a greater concentration of di-, or tri-, or 
tetrasubstituted olefinic epoxides in the exterior blocks, and lesser 
concentrations of these epoxides in the interior blocks of the polymer. 
The exterior blocks generally contain such epoxides within the 
concentration range of 0.2 to 10 milliequivalents of exterior block and 
the ratio of the concentration such epoxide groups in the exterior blocks 
to the concentration in the interior blocks is at least 3:1. The molecular 
weight of the exterior blocks ranges from 3000 to 50,000 and the molecular 
weight of the interior blocks ranges from 15,000 to 200,000. Such polymers 
are described in more detail in copending application Ser. No. 863,579, 
filed Apr. 3, 1992, entitled "Epoxidized Diene Elastomers for Exterior 
Block Crosslinking," which is herein incorporated by reference. A special 
case is where the exterior blocks are formed of polyisoprene polymerized 
under conditions that yield primarily 1,4-polyisoprene (trisubstituted) 
and the interior blocks are of polybutadiene (mono- or disubstituted). 
Another special case is where the exterior block is a random 
polystyrene-polyisoprene copolymer in which a majority of the polyisoprene 
is 1,4-polyisoprene and the interior block is polybutadiene. Such polymers 
give the advantage of localizing the crosslinking in the exterior blocks. 
The present invention provides improved adhesives, sealants, and coatings 
which have a phase separated structure after curing to a crosslinked 
network. Phase separation is important to achieve a hard reinforcing phase 
dispersed in a continuous rubber phase which gives reinforcing properties 
to the composition. Phase separation is achieved by inclusion in the 
second reactive component of segments that are phase separated after 
curing with the reactive diene polymers. The coreactive components include 
natural epoxy functional oils such as vernonia oil epoxidized linseed or 
soybean oil, and epoxidized linear, radial or star polymers having an 
epoxidized conjugated diene segment and a segment having a conjugated 
diene and a monoalkenyl aromatic hydrocarbon. In the epoxidized linear, 
radial or star coreactant, a monoalkenyl aromatic hydrocarbon content of 
20% by weight or greater is preferred, and a monoalkenyl aromatic 
hydrocarbon content of 30% by weight or greater is most preferred. 
The polymers containing conjugated dienes are prepared using anionic 
initiators or polymerization catalysts. Such polymers may be prepared 
using bulk, solution or emulsion techniques. In any case, the polymer 
containing at least ethylenic unsaturation will, generally, be recovered 
as a solid such as a crumb, a powder, a pellet or the like, but it also 
may be recovered as a liquid such as in the present invention. 
Conjugated dienes which may be polymerized anionically include those 
conjugated dienes containing from about 4 to about 24 carbon atoms such as 
1,3-butadiene, isoprene, piperylene, methylpentadiene, phenyl-butadiene, 
3,4-dimethyl-1,3-hexadiene, 4,5-diethyl-1,3-octadiene and the like. 
Isoprene and butadiene are the preferred conjugated diene monomers for use 
in the present invention because of their low cost and ready availability. 
Monoalkenyl aromatic compounds which may be copolymerized with the 
conjugated dienes in the coreactive polymers include vinyl aryl compounds 
such as styrene, various alkyl-substituted styrenes, alkoxy-substituted 
styrenes, vinyl napthalene, alkyl-substituted vinyl napthalenes and the 
like. 
The preferred epoxidized polymers have an epoxide equivalent weight of 
between about 10,000 and about 333. The polymers may then be crosslinked 
through at least some of the epoxy functionality. 
The epoxidized copolymers of this invention can be prepared by the 
epoxidation procedures as generally described or reviewed in the 
Encyclopedia of Chemical Technology 19, 3rd ed., 251-266 (1980), D. N. 
Schulz, S. R. Turner, and M. A. Golub, Rubber Chemistry and Technology, 5, 
809 (1982), W-K. Huang, G-H. Hsuie, and W-H. Hou, Journal of Polymer 
Science, Part A: Polymer Chemistry, 26, 1867 (1988), and K. A. Jorgensen, 
Chemical Reviews, 89, 431 (1989), and Hermann, Fischer, and Marz, Angew. 
Chem. Int. Ed. Engl. 30 (No. 12), 1638 (1991), all of which are 
incorporated by reference. 
For instance, epoxidation of the base polymer can be effected by reaction 
with organic peracids which can be preformed or formed in situ. Suitable 
preformed peracids include peracetic and perbenzoic acids. In situ 
formation may be accomplished by using hydrogen peroxide and a low 
molecular weight carboxylic acid such as formic acid. Alternatively, 
hydrogen peroxide in the presence of acetic acid or acetic anhydride and a 
cationic exchange resin will form a peracid. The cationic exchange resin 
can optionally be replaced by a strong acid such as sulfuric acid or 
p-toluenesulfonic acid. The epoxidation reaction can be conducted directly 
in the polymerization cement (polymer solution in which the polymer was 
polymerized) or, alternatively, the polymer can be redissolved in an inert 
solvent such as toluene, benzene, hexane, cyclohexane, methylenechloride 
and the like and epoxidation conducted in this new solution or can be 
epoxidized neat. Epoxidation temperatures on the order of 0.degree. to 
130.degree. C. and reaction times from 0.1 to 72 hours may be utilized. 
When employing hydrogen peroxide and acetic acid together with a catalyst 
such as sulfuric acid, the product can be a mixture of epoxide and hydroxy 
ester. The use of peroxide and formic acid in the presence of a strong 
acid may result in diolefin polymer blocks containing both epoxide and 
hydroxy ester groups. Due to these side reactions caused by the presence 
of an acid, it is preferable to carry out the epoxidation at the lowest 
possible temperature and for the shortest time consistent with the desired 
degree of epoxidation. Epoxidation may also be accomplished by treatment 
of the polymer with hydroperoxides or oxygen in the presence of transition 
metals such as Mo, W, Cr, V and Ag, or with methyl-trioxorhenium/hydrogen 
peroxide with and without amines present. .sup.1 H NMR is an effective 
tool to determine which and how much of each type of olefinic double bond 
(ODB) is epoxidized. Further, the amount epoxy can also be measured by the 
direct titration with perchloric acid (0.1N) and quaternary ammonium 
halogenide (tetraethyl-ammonium bromide) where the sample is dissolved in 
methylene chloride. Epoxy titration is described in Epoxy Resins Chemistry 
and Technology, edited by Clayton A. May and published in 1988 (p. 1065) 
which is herein incorporated by reference. 
The polymers of this invention are preferably cured (crosslinked) by 
ultraviolet or electron beam radiation, but radiation curing utilizing a 
wide variety of electromagnetic wavelengths is feasible. Either ionizing 
radiation such as alpha, beta, gamma, X-rays and high energy electrons or 
non-ionizing radiation such as ultraviolet, visible, infrared, microwave 
and radio frequency may be used. 
The polymers may also be cured without the use of radiation by addition of 
a cationic initiator. Suitable initiators include the halides of tin, 
aluminum, zinc, boron, silicon, iron, titanium, magnesium and antimony, 
and the fluoroborates of many of these metals. BF.sub.3 complexes such as 
BF.sub.3 ether and BF.sub.3 -amine are included. Also useful are strong 
Bronsted acids such as trifluoromethanesulfonic (triflic acid) and the 
salts of triflic acid such as FC-520 (3M Company). The cationic initiator 
is chosen to be compatible with the polymer being crosslinked, the method 
of application and cure temperature. The epoxy-containing polymers may 
also be crosslinked by the addition of multifunctional carboxylic acids, 
acid anhydrides, and alcohols, and in general by the curing methods 
described in U.S. Pat. No. 3,970,608, which is incorporated by reference. 
Volatile amines can be used to inhibit or retard unwanted cure, such as to 
maintain fluidity in one pack formulations until they are applied and 
reach the appropriate bake temperature for cure. They may also be cured by 
use of amino resins in the presence of a proton donating acid. Radiation 
crosslinking is preferred because reactive ingredients do not come in 
contact with warm adhesives. 
The crosslinked materials of the present invention are useful in adhesives 
(including pressure sensitive adhesives, contact adhesives, laminating 
adhesives and assembly adhesives), sealants, coatings, films (such as 
those requiring heat and solvent resistance), printing plates, fibers, and 
as modifiers for polyesters, polyethers and polyamides. The polymers are 
also useful in asphalt modification. In addition to the functionalized 
polymer and any curing aids or agents, products formulated to meet 
performance requirements for particular applications may include various 
combinations of ingredients including adhesion promoting or tackifying 
resins, plasticizers, fillers, solvents, stabilizers, etc. as described in 
detail in the aforementioned commonly assigned applications which are 
incorporated by reference. 
Compositions of the present invention are typically prepared by blending 
the components, preferably between 25.degree. C. and 200.degree. C., until 
a homogeneous blend is obtained, usually less than three (3) hours. 
Various methods of blending are known to the art and any method that 
produces a homogeneous blend is satisfactory. The resultant compositions 
may then preferably be used in a wide variety of applications. 
Alternatively, the ingredients may be blended into a solvent. 
Adhesive compositions of the present invention may be utilized as many 
different kinds of adhesives, for example, laminating adhesives, flexible 
packaging laminated adhesives, pressure sensitive adhesives, tie layers, 
hot melt adhesives, solvent borne adhesives and waterborne adhesives in 
which the water has been removed before curing. The adhesive can consist 
of simply the epoxidized polymer or, more commonly, a formulated 
composition containing a significant portion of the epoxidized polymer 
along with other known adhesive composition components. A preferred method 
of application will be warm melt application at a temperature 20.degree. 
to 130.degree. C. because warm melt application is non-polluting and can 
be used on heat sensitive substrates. The adhesive can be heated before 
and after cure to further promote cure or post cure. Radiation cure of 
warm adhesive is believed to promote faster cure than radiation cure at 
room temperature. 
Preferred uses of the present formulation are in the preparation of 
pressure-sensitive adhesive tapes, the manufacture of labels or flexible 
packaging, and strippable coatings. The pressure-sensitive adhesive tape 
comprises a flexible backing sheet and a layer of the adhesive composition 
of the instant invention coated on one major surface of the backing sheet. 
The backing sheet may be a plastic film, paper or any other suitable 
material and the tape may include various other layers or coatings, such 
as primers, release coatings and the like, which are used in the 
manufacture of pressure-sensitive adhesive tapes. Alternatively, when the 
amount of tackifying resin is zero, the compositions of the present 
invention may be used for adhesives that do not tear paper and molded 
goods and the like.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention is preferably a radiation curable composition, 
containing approximately equal amounts of an epoxidized radial polymer and 
a terpene tackifying resin, and from 5 to 15% by weight of an epoxidized 
polymer which results in phase separation. Higher amounts of the second 
reactive polymer increases the viscosity of the blend. 
A most preferred reactive polymer is an epoxidized linear polymer having 
the structure epoxidized isoprene-styrene/hydrogenated 
butadiene-epoxidized isoprene. The epoxidized linear polymer is produced 
by hydrogenating and then epoxidizing a linear 
isoprene-styrene/butadiene-isoprene block copolymer wherein the 
styrene/butadiene block is random or tapered to improve phase separation 
with minimum impact on viscosity. 
Preferred epoxidized radial polymers which are useful in the present 
invention consist of conjugated diene blocks that are coupled in a star 
arrangement. The star polymers are preferably lightly epoxidized near the 
end of the polymeric arms and are preferably hydrogenated to remove 
remaining unsaturation. 
The polymers described immediately above are relatively high molecular 
weight, low viscosity materials. Blocks comprising predominantly 
conjugated diolefin monomer units generally will have peak molecular 
weights between about 1000 and about 17,000 prior to epoxidation. 
For anionically polymerized linear polymers, the polymer is essentially 
monodisperse and it is both convenient and adequately descriptive to 
report the "peak" molecular weight of the narrow molecular weight 
distribution usually observed for the linear polymer or polymeric arm 
instead of true or average molecular weights. Measurement of the true 
molecular weight of the final coupled radial polymer is not as 
straightforward or as easy to make using GPC. This is because the star 
shaped molecules do not separate and elute through the packed GPC columns 
in the same manner as do the linear polymers used for the calibration, 
and, hence, the time of arrival at a UV or refractive index detector is 
not a good indicator of the molecular weight. A good method to use for a 
star polymer is to measure the weight average molecular weight by light 
scattering techniques. The sample is dissolved in a suitable solvent at a 
concentration less than 1.0 gram of sample per 100 milliliters of solvent 
and filtered using a syringe and porous membrane filters of less than 0.5 
microns pore size directly into the light scattering cell. The light 
scattering measurements are performed as a function of scattering angle 
and of polymer concentration using standard procedures. The differential 
refractive index (DRI) of the sample is measured at the same wave length 
and in the same solvent used for the light scattering. 
The coreactive polymer blends of this invention are preferably cured by 
ultraviolet radiation, but radiation curing utilizing a wide variety of 
electromagnetic wavelength is feasible. 
When using non-ionizing radiation it is necessary to employ a 
photoinitiator to initiate the crosslinking reaction. Useful 
photoinitiators include diaryliodonium, alkoxy-substituted diaryliodonium, 
triarylsulfonium, dialkylphenacylsulfonium, and 
dialkyl-4-hydrophenysulfonium salts. The anions in these salts generally 
possess low nucleophilic character and include SbF.sub.6 -, BF.sub.4 -, 
PF.sub.6 - and AsF.sub.6 -. Specific examples include 
(4-octyloxyphenyl)-phenyl-iodium hexafluoroantimonate, UVI-6990 (from 
Union Carbide), and FX-512 (3M Company). UVI-6974, an aryl sulfonium salt 
from Union Carbide, and bis(dodecylphenyl)iodonium hexaflouroantimonate, 
UV9310C (from General Electric) are especially effective. The salts can be 
used alone or in conjunction with a photosensitizer to respond to long 
wave length UV and visible light. Examples of photosensitizers include 
thioxanthone, anthracene, perylene, phenothiazione, 1,2-benzathracene 
coronene, pyrene and tetracene. The photoinitiator and photosensitizer are 
chosen to be compatible with the polymer being crosslinked and the light 
source available. 
Radiation induced cationic curing may also be done in combination with free 
radical curing. Free radical curing can be further enhanced by the 
addition of additional free radical photoinitiators and photosensitizers 
for them. 
In the radiation crosslinked compositions of the present invention, 
including adhesives, coatings and sealants, it is usual to add an adhesion 
promoting or tackifying resin that is compatible with the polymer. The 
prior art, as exemplified by U.S. Pat. No. 4,135,031, teaches that 
hydrogenated rosins, esters of rosins and other rosin materials are very 
compatible with epoxidized diene polymers. This indeed appears to be true. 
However, the prior art evidently did not attempt to radiation crosslink 
the compositions described including epoxidized diene polymers and rosin 
tackifying resins. The rosin materials interfere with the cure of the 
composition and thus were not desirable for use in the radiation 
crosslinked compositions of the present invention. 
Preferred tackifying resins include a diene-olefin copolymer of piperylene 
and 2-methyl-2-butene having a softening point of about 95.degree. C., 
commercially available as Wingtack.RTM. 95, hydrogenated polystyrene or 
polyalphamethylstyrene resins such as Regalrez.RTM. 1094 resin from 
Hercules, and terpene resins. 
The Applicants herein have found that terpene tackifying resins are very 
compatible with the epoxidized polymers used in the present invention. 
Terpene tackifying resins include terpene itself (C.sub.10 H.sub.16) which 
is an unsaturated hydrocarbon occurring in most essential oils and oleo 
resins of plants. The terpenes are based on the isoprene unit H.sub.2 
C.dbd.C(CH.sub.3)--C(H).dbd.CH.sub.2 and may be either acyclic or cyclic 
with one or more benzenoid groups. They are classified as monocyclic 
(dipentene), dicyclic (pinene), or acyclic (myrcene). Also included are 
styrenated terpenes and polyterpene resins. Specific examples of 
commercially available polyterpenes which can be used herein are 
Piccolyte.RTM. A115, A125 and A135 resins made by Hercules which are 
produced from the terpene monomer .alpha.-pinene and the Zonatac.RTM. 
resins made by Arizona. The terpene resins will generally be used in the 
range of 20 to 400 parts of terpene resin per 100 parts of polymer (by 
weight), preferably 30 parts to 200 parts. 
Epoxidized terpenes may also be used in the present invention as the 
tackifying resin. Terpenes may be epoxidized in the same manner as the 
polymer is epoxidized. The epoxidized terpenes work as well as 
unepoxidized terpenes and in some cases it appears that there are 
advantages to using epoxidized terpenes. 
A composition of the instant invention may contain plasticizers, such as 
rubber extending plasticizers, or compounding oils or organic or inorganic 
pigments and dyes. Rubber compounding oils are well-known in the art and 
include both high saturates content oils and high aromatics content oils. 
Preferred plasticizers are highly saturated oils, e.g. Tufflo.RTM. 6056 
and 6204 oil made by Arco and process oils, e.g. Shellflex.RTM. 371 oil 
made by Shell. The amounts of rubber compounding oil employed in the 
invention composition can vary from 0 to about 500 phr, preferably between 
about 0 to about 100 phr, and most preferably between about 0 and about 60 
phr. 
Optional components of the present invention are stabilizers which inhibit 
or retard heat degradation, oxidation, skin formation and color formation. 
Stabilizers are typically added to the commercially available compounds in 
order to protect the polymers against heat degradation and oxidation 
during the preparation, use and high temperature storage of the adhesive 
composition. 
Various types of fillers and pigments can be included in the coating or 
sealant formulation. This is especially true for exterior coatings or 
sealants in which fillers are added not only to create the desired appeal 
but also to improve the performance of the coatings or sealant such as its 
weatherability. A wide variety of fillers can be used. Suitable fillers 
include calcium carbonate, clays, talcs, zinc oxide, titanium dioxide and 
the like. The amount of filler usually is in the range of 0 to about 65% w 
based on the solvent free portion of the formulation depending on the type 
of filler used and the application for which the coating or sealant is 
intended. An especially preferred filler is titanium dioxide. 
If the coating or sealant will be applied from solvent solution, the 
organic portion of the formulation will be dissolved in a solvent or blend 
of solvents. Aromatic hydrocarbon solvents such as toluene, xylene, or 
Shell Cyclo Sol 53 are suitable. Aliphatic hydrocarbon solvents such as 
hexane, naphtha or mineral spirits may also be used. If desired, a solvent 
blend consisting of a hydrocarbon solvent with a polar solvent can be 
used. Suitable polar solvents include esters such as isopropyl acetate, 
ketones such as methyl isobutyl ketone, and alcohols such as isopropyl 
alcohol. The amount of polar solvent used depends on the particular polar 
solvent chosen and on the structure of the particular polymer used in the 
formulation. Usually, the amount of polar solvent used is between 0 and 
50% w in the solvent blend. 
Additional stabilizers known in the art may also be incorporated into the 
adhesive composition. These may be for protection during the life of the 
article against, for example, oxygen, ozone and ultra-violet radiation. 
However, these additional stabilizers should be compatible with the 
essential stabilizers mentioned hereinabove and their intended function as 
taught herein. 
The adhesive, coating and sealant compositions of the present invention are 
typically prepared by blending the components at an elevated temperature, 
preferably between about 50.degree. C. and about 200.degree. C., until a 
homogeneous blend is obtained, usually less than three (3) hours. Various 
methods of blending are known to the art and any method that produces a 
homogeneous blend is satisfactory. The resultant compositions may then 
preferably be used in a wide variety of applications. Alternatively, the 
ingredients may be blended into a solvent. 
The adhesive compositions of the present invention may be utilized as many 
different kinds of adhesives, for example, laminating adhesives, pressure 
sensitive adhesives, tie layers, hot melt adhesives, solvent borne 
adhesives and waterborne adhesives in which the water has been removed 
before curing. The adhesive can consist of simply the epoxidized polymer 
or, more commonly, a formulated composition containing a significant 
portion of the epoxidized polymer along with other known adhesive 
composition components. A preferred method of application will be hot melt 
application at a temperature around or above 100.degree. C. because hot 
melt application above 100.degree. C. minimizes the presence of water and 
other low molecular weight inhibitors of cationic polymerization. The 
adhesive can be heated before and after cure to further promote cure or 
post cure. Radiation cure of hot adhesive is believed to promote faster 
cure than radiation cure at lower temperatures. 
Preferred uses of the present formulation are the preparation of 
pressure-sensitive adhesive tapes and the manufacture of labels. The 
pressure-sensitive adhesive tape comprises a flexible backing sheet and a 
layer of the adhesive composition of the instant invention coated on one 
major surface of the backing sheet. The backing sheet may be a plastic 
film, paper or any other suitable material and the tape may include 
various other layers or coatings, such as primers, release coatings and 
the like, which are used in the manufacture of pressure-sensitive adhesive 
tapes. Alternatively, when the amount of tackifying resin is zero, the 
compositions of the present invention may be used for adhesives that do 
not tear paper and molded goods and the like. 
Coating compositions are useful for strippable coatings for protecting 
metal products prior to use, high friction coatings, waterproofing 
coatings, shatter retentive coatings, coating for optical fibers, etc. 
Sealant compositions are useful for insulated glass windows, construction 
sealants, corrosion protective sealants (i.e. weldable sealants for the 
automotive industry, etc.), etc. 
EXAMPLE 1 (Comparison) 
This example demonstrates, for comparison to the present invention, a 
crosslinked pressure sensitive adhesive layer containing an epoxidized 
star polymer as described in U.S. Pat. No. 5,229,464. The epoxidized 
polymer used in this example is an epoxidized isoprene-butadiene star 
polymer (205) having an arm molecular weight of 5600, approximately 13 
arms and an epoxy content of 0.65 Meq per gram of polymer. Coreactants 
such as other epoxidized polymers or epoxidized diluents or reactive 
diluents are absent from the formulation of this example. 
An adhesive composition containing 49.6 wt % of the epoxidized star 
polymer, 49.6 wt % of Zonatac.RTM. 105L thermoplastic modified terpene 
hydrocarbon resin from Arizona Chemical Company, 0.5 wt % of UVI 6974 
photoinitiator, and 0.3 wt % of Irganox 1010 antioxidant was cast from 
tetrahydrofuran (THF) onto a 1 mil polyester backing film. The coated film 
was prebaked for 2 minutes at 121.degree. C. to simulate a warm 
application and UV cured at 30 feet per minute under a single medium 
pressure mercury lamp. The adhesive layer changed from a sticky, viscous 
state to a tacky state having good internal strength. The adhesive was 
postbaked for 10 minutes at 121.degree. C. to assure full cure to ultimate 
properties. 
The adhesive layer had the following properties which are typically 
measured for pressure sensitive adhesives. 
______________________________________ 
Film Appearance Clear 
Feel Tacky 
Polymer Gel Content 74% 
Polyken Probe Tack.sup.1 0.67 Kg 
TLMI Loop Tack 1.6 pli 
180.degree. Peel from Steel 
3.9 pli 
Holding Power to Steel.sup.2 at 23.degree. C. 
54 hrs. 
______________________________________ 
.sup.1 Adhesion lost between the adhesive layer and the polyester backing 
.sup.2 Tested with 1 in. .times. 1 in. overlap and a 2 Kg weight. 
Importantly, this cured formulation appeared clear. Blends or formulations 
which are not phase separated are clear. Since this formulation is clear, 
phase separation is not suggested. Therefore, the balance of properties 
achieved with the cured formulation of this example is representative of 
adhesives not having phase separation. The following adhesive layers were 
prepared by the same process except that a coreactant is incorporated at 
an amount of 10% of the total weight of the adhesive composition. 
EXAMPLE 2 
This example demonstrates a crosslinked pressure sensitive adhesive 
prepared from epoxidized star polymers and a coreactant as described in 
the present application. The adhesive composition contains 44.6 wt % of 
the epoxidized star polymer of Example 1, 44.6 wt % of the Zonatac.RTM. 
105L resin, 10 wt % of vernonia oil which is a natural epoxy functional 
oil having about 3 epoxies per molecule, 0.5 wt % of UVI 6974 
photoinitiator, and 0.3 wt % Irganox 1010 antioxidant was cast from 
tetrahydrofuran (THF) onto a 1 mil polyester backing film. The coated film 
was prebaked for 2 minutes at 121.degree. C. to simulate a warm 
application and UV cure at 30 feet per minute under a single medium 
pressure mercury lamp. The adhesive layer changed from a sticky, viscous 
state to a tacky state having good internal strength. The adhesive was 
postbaked for 10 minutes at 121.degree. C. to assure full cure to ultimate 
properties. 
The adhesive layer had the following properties which are typically 
measured for pressure sensitive adhesives. 
______________________________________ 
Film Appearance Slightly Hazy 
Feel Tacky 
Polymer Gel Content 75% 
Polyken Probe Tack 0.69 Kg 
TLMI Loop Tack 3.4 pli 
180.degree. Peel from Steel 
2.1 pli 
Holding Power to Steel.sup.1 at 23.degree. C. 
&gt;67 hrs. 
Shear Adhesion Failure Temp..sup.2 
&gt;143.degree. C. 
______________________________________ 
.sup.1 Tested with 1 in. .times. 1 in. overlap and 2 Kg weight. 
.sup.2 Tested with 1 in. .times. 1 in. overlap and 500 g weight. 
This coreactive pressure sensitive adhesive composition had an excellent 
balance of properties attributed to phase separation during crosslinking. 
The cured composition is judged phase separated because of the slightly 
hazy appearance. Incorporation of the coreactive vernonia oil yielded a 
pressure sensitive adhesive with excellent adhesion above 143.degree. C. 
at high shear and enhanced tack properties. 
EXAMPLE 3 
This example demonstrates a crosslinked pressure sensitive adhesive 
prepared from epoxidized star polymers and a coreactant as described in 
the present application. The adhesive composition contains 44.6 wt % of 
the epoxidized star polymer of Example 1, 44.6 wt % of the Zonatac.RTM. 
105L resin, 10 wt % of an epoxidized linear polymer (204) having the 
structure epoxidized isoprene-hydrogenated styrene/butadiene-epoxidized 
isoprene with a peak molecular weight of 6,000 available from Shell 
Chemical Company, 0.5 wt % of UVI 6974 photoinitiator, and 0.3 wt % of 
Irganox 1010 antioxidant was cast from tetrahydrofuran (THF) onto a 1 mil 
polyester backing film. The coated film was prebaked for 2 minutes at 
121.degree. C. to simulate a warm application and UV cure at 30 feet per 
minute under a single medium pressure mercury lamp. The adhesive layer 
changed from a sticky, viscous state to a tacky state having good internal 
strength. The adhesive was postbaked for 10 minutes at 121.degree. C. to 
assure full cure to ultimate properties. 
The adhesive layer had the following properties which are typically 
measured for pressure sensitive adhesives. 
______________________________________ 
Film Appearance Cloudy 
Feel Tacky 
Polymer Gel Content 70% 
Polyken Probe Tack 0.46 Kg 
TLMI Loop Tack 3.4 pli 
180.degree. Peel from Steel 
2.0 pli 
Holding Power to Steel.sup.1 at 23.degree. C. 
&gt;67 hrs. 
Shear Adhesion Failure Temp..sup.2 
&gt;143.degree. C. 
______________________________________ 
.sup.1 Tested with 1 in. .times. 1 in. overlap and 2 Kg weight. 
.sup.2 Tested with 1 in. .times. 1 in. overlap and 500 g weight. 
This coreactive pressure sensitive adhesive composition had an excellent 
balance of properties attributed to phase separation during crosslinking. 
The cured composition is judged phase separated because of the cloudy 
appearance. In comparison to Example I which had excellent tack and 
adhesion failure at room temperature under low shear, the composition of 
Example 3, which had incorporated a coreacting linear epoxidized polymer, 
had moderate tack and retained adhesion above 143.degree. C. at high 
shear. Incorporation of the coreacting polymer (204) yielded a pressure 
sensitive adhesive with excellent adhesion above 143.degree. C. at high 
shear and enhanced tack property. 
EXAMPLE 4 
This example demonstrates a strippable coating prepared from epoxidized 
star polymers and a coreactant as described in the present application. 
The adhesive composition contains 44.6 wt % of the epoxidized star polymer 
of Example 1, 44.6 wt % of the Zonatac.RTM. 105 L resin, 10 wt % of 
Drapex.RTM. 6.8 epoxidized soybean oil from Witco Chemical, 0.5 wt % of 
UVI 6974 photoinitiator, and 0.3 wt % of Irganox 1010 antioxidant was cast 
from tetrahydrofuran (THF) onto a 1 mil polyester backing film. The coated 
film was prebaked for 2 minutes at 121.degree. C. to simulate a warm 
application and UV cure at 30 feet per minute under a single medium 
pressure mercury lamp. The coating layer changed from a sticky, viscous 
state to a tacky state having good internal strength. The coating was 
postbaked for 10 minutes at 121.degree. C. to assure full cure to ultimate 
properties. 
The coating layer had the following properties which are typically measured 
for strippable coatings. 
______________________________________ 
Film Appearance Slightly Hazy 
Feel Tacky to Cohesive 
Polymer Gel Content 69% 
Polyken Probe Tack 0.03 Kg 
TLMI Loop Tack 0.5 pli 
180.degree. Peel from Steel 
3.8 pli 
Holding Power to Steel.sup.1 at 23.degree. C. 
&gt;46 hrs. 
Shear Adhesion Failure Temp..sup.2 
&gt;96.degree. C. 
______________________________________ 
.sup.1 Tested with 1 in. .times. 1 in. overlap and 2 Kg weight. 
.sup.2 Tested with 1 in. .times. 1 in. overlap and 500 g weight. 
This coreactive strippable coating composition had excellent strength and 
poor tack attributed to phase separation during crosslinking. The cured 
composition is judged phase separated because of the slightly hazy 
appearance. A similar composition prepared with Drapex.RTM. 10.4 
epoxidized linseed oil had lower peel strength at 2.0 pli. 
EXAMPLE 5 (Comparison) 
This example demonstrates the need to sometimes use two or more 
photoinitiators to ensure solubility in all phases of the formulation so 
that all phases are crosslinked when making adhesives or coatings from 
epoxidized star polymers. The adhesive composition contains 44.6 wt % of 
the epoxidized star polymer of Example 1, 44.6 wt % of the Zonatac.RTM. 
105 L resin, 10 wt % of URV 6110 cycloaliphatic diepoxide from Union 
Carbide, 0.5 wt % of UVI 6974 photoinitiator, and 0.3 wt % of Irganox 1010 
antioxidant was cast from tetrahydrofuran (THF) onto a 1 mil polyester 
backing film. The coated film was prebaked for 2 minutes at 121.degree. C. 
to simulate a warm application and UV cure at 30 feet per minute under a 
single medium pressure mercury lamp. The adhesive layer had no measurable 
gel content after curing which is attributed to selective absorbance of 
the photoinitiator into the cycloaliphatic diepoxide which cured as fine 
particles that passed through the 100 mesh screen used to collect the gel. 
In other words, the minor phase was selectively cured leaving an uncured 
major phase which was easily dissolved in solvent. The same result was 
obtained by replacing the URV 6110 cycloaliphatic diepoxide with ERL 4234 
cycloaliphatic diepoxide from Union Carbide.