Poly(.beta.-hydroxyorganoate) pressure sensitive adhesive compositions

The present invention provides pressure sensitive adhesives, compositions from which the pressure sensitive adhesives are formed, and articles having therein these pressure sensitive adhesives. The pressure sensitive adhesives, which have a Tg of less than about 20.degree. C., include a poly(.beta.-hydroxyorganoate) or mixture thereof. Preferably, these poly(.beta.-hydroxyorganoate)s include monomeric units of the general formula: ##STR1## wherein: a minor amount (preferably no greater than about 20 mole percent) of the monomeric units have an R group containing 1-3 carbon atoms; and a major amount (preferably at least about 80 mole percent) of the monomeric units have an R group containing 4-30 (preferably 4-20) carbon atoms.

FIELD OF THE INVENTION 
The invention relates to pressure-sensitive adhesive compositions 
containing poly(.beta.-hydroxyorganoate)s. 
BACKGROUND OF THE INVENTION 
Tacky pressure-sensitive adhesive ("PSA") compositions suitable for use in 
adhesive tapes, for example, must have a requisite four-fold balance of 
adhesion, cohesion, stretchiness, and elasticity, an open time tack (i.e., 
period of time during which the adhesive is tacky at room temperature) on 
the order of days and often months or years, and a glass transition 
temperature (Tg) of less than about 20.degree. C. PSA-coated tapes have 
been produced for at least 50 years, however, early PSA-coated tapes did 
not have very desirable characteristics. Early PSA tapes were merely 
expected to temporarily adhere to a surface upon which they were adhered. 
Adhesive failure, discoloration, and cohesive failure were tolerated. 
Today, PSAs are expected to possess this extremely delicate balance of 
properties known in the trade as the "four-fold" balance of adhesion, 
cohesion, stretchiness, and elasticity. Some PSA compositions also have 
desirable transparency and resistance to aging, even upon exposure to 
severe weathering conditions. 
Pressure sensitive adhesives have historically been based on 
petroleum-derived polymers such as poly(ethylene), poly(propylene), 
ethylene-vinyl acetate copolymers, and styrene block copolymers, for 
example. These compositions are typically further tackified, plasticized, 
and reinforced with a variety of resins, oils, and waxes, which are 
derived from both petroleum and naturally occurring feedstocks such as 
wood, gum, terpenes, etc. For example, early PSA compositions consisted of 
natural crude rubber tackified by esterfied wood rosin. However, these 
PSAs had poor aging properties, e.g., poor oxidative stability. These 
compositions were improved by the introduction of synthetic acrylic ester 
polymers, which were inherently tacky and possessed the elasticity and 
compliance required for the four-fold balance of properties. As the need 
arose, improvements were made in the basic acrylic ester PSA to meet the 
needs in the marketplace. Transparency and resistance to oxidation 
inherent in acrylic ester PSAs made them outstanding candidates for the 
most demanding PSA tape applications. 
Environmental factors are becoming increasingly important in products 
marketed to consumers such as PSA containing diaper tapes, packaging 
tapes, medical tapes, surgical drapes, and the like. Two very important 
environmental factors are the mode of production and the mode of disposal 
of such products. For example, during manufacture, it is important to use 
solvent-free processing. Additionally, with the trend toward 
environmentally degradable materials, a PSA that could be disposed in an 
environmentally sound manner (e.g., in a municipal solid waste compost 
site) would be an important feature. The classic composition of PSAs are 
generally resistant to degradation upon disposal in such an environment. 
In addition to resisting degradation themselves, classic PSA materials can 
inhibit the degradation of the substrates on which they are coated. Thus, 
what is needed are PSAs, i.e., adhesives having the four-fold balance of 
properties described above, composed of biodegradable polymers. 
Although hot melt adhesives, and even "pressure sensitive hot melt 
adhesives" (which are to be adhesives having a finite open time and 
lacking the four-fold balance of PSAs) composed of biodegradable polymers 
have been reported, little has been done in the area of biodegradable 
pressure sensitive adhesives. See, for example, U.S. Pat. Nos. 5,169,889 
(Kauffman et al.) and 5,252,646 (Iovine et al.), which describe hot melt 
adhesives, varying from pressure sensitive to nonpressure sensitive in 
character, containing either poly(lactide) homoor copolymers or a linear 
polyester of 3-hydroxybutyric (HB) and 3-hydroxyvaleric acids (HV). The 
copolyesters, P(HB-co-HV), are statistically random and of high 
crystallinity (&gt;60%) throughout a range of compositions varying from 0 to 
47 mol-% HV. See, for example, R. A. Gross et al., Macromolecules, 22, 
1106-1115 (1989). 
SUMMARY OF THE INVENTION 
The present invention stems from the growing movement towards products that 
have demonstrated some level of biodegradation. The present invention 
utilizes a class of naturally occurring, thermoplastic, biodegradable 
polymers. These biodegradable polymers are generally compostable, i.e., 
capable of undergoing substantial conversion by microorganisms under 
aerobic conditions to carbon dioxide, water, and biomass. It is believed 
that at least some of these polymers are also degradable under anaerobic 
conditions. 
This class of polymers encompasses poly(hydroxyorganoate)s, i.e., 
poly(.beta.-hydroxyorganoate)s, which possess thermal and oxidative 
stability, and chemical resistance. They are generally nontoxic and safe 
in use and upon disposal. They also possess a wide range of adhesive 
properties, particularly when formulated with an appropriate tackifier. 
These properties make suitable for use in pressure sensitive adhesives for 
a wide range of applications where it is desirable to have independent 
control of peel and shear adhesion, and where the ultimate disposal of the 
adhesive will be into a biologically active environment where 
biodegradation will be allowed to occur. Compositions with improved PSA 
properties may be made by blending two or more such polymers or by 
crosslinking. 
The present invention provides pressure sensitive adhesives, compositions 
from which the pressure sensitive adhesives are formed, and articles 
having a substrate with at least one surface on which is coated these 
pressure sensitive adhesives. The pressure sensitive adhesives, which have 
a Tg of less than about 20.degree. C., include a 
poly(.beta.-hydroxyorganoate) or mixture thereof. Preferably, these 
poly(.beta.-hydroxyorganoate)s include monomeric units of the general 
formula: 
##STR2## 
wherein: a minor amount (preferably no greater than about 20 mole percent) 
of the monomeric units have an R group containing 1-3 carbon atoms; and a 
major amount (preferably at least about 80 mole percent) of the monomeric 
units have an R group, i.e., side chain, containing 4-30 (preferably 4-20) 
carbon atoms. Particularly preferred embodiments include a 
poly(.beta.-hydroxyorganoate) having a major amount of at least two 
different monomeric units with R groups containing 4-30 carbon atoms. The 
adhesive compositions of the invention can be applied to a variety of 
substrates by a wide range of processes, i.e., solution coating, solution 
spraying, thermal extrusion, emulsion coating, etc., to make adhesive 
articles, e.g., tapes, adhesive transfer films, surgical drapes, and the 
like. 
As used in this invention: 
"polymer" means a homopolymer or a copolymer (i.e., a polymer containing 
two or more dissimilar, i.e., different, monomers), which includes a 
terpolymer, a tetrapolymer, and the like; copolymers derived from more 
than one type of monomer may be either random or block copolymers; 
"tackifier" means a low molecular weight (typically having a molecular 
weight of less than 2000 g/mol.), high glass transition temperature (Tg) 
resin (typically having a Tg of greater than 50.degree. C.) used to 
control the adhesive tack of a polymer; 
"crosslinking agent" means a compound that either initiates a crosslinking 
process or connects polymer chains and becomes incorporated therein; this 
increases the molecular weight of the adhesive and thus its cohesive 
strength without unduly affecting its compliance or other PSA properties; 
this encompasses thermally or radiation activated crosslinkers, 
photoinitiators, sensitizers, ect. 
"chemical crosslinker" means a compound which, under the influence of heat 
or light, connects polymer chains and becomes incorporated therein; 
"radiation crosslinker" or "radiation active (or activated) crosslinker" 
means a compound which, under the influence of radiation, connects polymer 
chains and becomes incorporated therein; 
"sensitizer" means a material that absorbs energy and transfers energy to a 
different material in an activation process; 
"photoinitiator" means a material that has the ability to produce radicals 
upon exposure to light; and 
"thermal initiator" means a material that has the ability to produce 
radicals upon exposure to heat. 
As these crosslinking agents are defined, it should be apparent that some 
of the categories overlap such that certain compounds can be classified in 
more than one category. Thus, a thermal initiator could also be a chemical 
crosslinker, for example.

DETAILED DESCRIPTION 
The present invention provides tacky PSA compositions and adhesive coated 
materials having the requisite four-fold balance of adhesion, cohesion, 
stretchiness, and elasticity, open time on the order of days, and a Tg of 
less than about 20.degree. C. The adhesive compositions also have good 
peel strength and tack properties plus excellent shear strength and creep 
resistance, as well as excellent processability, with or without solvent. 
Generally, the adhesive compositions of the present invention also have 
optical clarity. The compositions of the present invention are generally 
resistant to oxidative and photochemical degradation for the anticipated 
use life of the PSA, although they will undergo degradation upon exposure 
to biologically active environments. 
The PSA compositions of the present invention preferably have a peel 
adhesion of at least about 1.0N/dm, preferably at least about 10N/dm. 
Thus, the PSA compositions of the present invention can be repositionable 
pressure sensitive adhesives. More preferably, the PSA compositions of the 
present invention also have a static shear of at least about 1 minute 
(preferably at least about 10 minutes, and more preferably at least about 
25 minutes). They also have an open time at room temperature (i.e., 
20.degree.-30.degree. C.), i.e., period of time during which the adhesive 
remains tacky, of at least about 7 days, preferably at least about 20 
days, more preferably at least about 30 days, most preferably at least 
about 6 months. Particularly preferred PSA compositions have an opent time 
of at least about 1 year. 
The PSA compositions of the present invention include a 
poly(.beta.-hydroxyorganoate), i.e., poly(hydroxyorganoate) or 
poly(3-hydroxyorganoate), or a mixture of various types of such polymers. 
Poly(.beta.-hydroxyorganoate)s are a class of 
.beta.-monoalkyl-substituted-poly-.beta.-esters that are naturally 
occurring in a wide variety of bacterial microorganisms. These polyesters 
function as intracellular carbon and energy storage materials. They are 
biodegradable polymers. 
Various bacteria, e.g., Pseudomonas oleovorans, Pseudomonas putida, 
Pseudomonas aeruginosa, Alcaligenes eutrophus , Rhodospirillum rubrum, 
Bacillus megaterium are capable of metabolizing alkanes, alkanols, 
alkanoic acids, alkenes, alkenols, alkenoic acids, and esters, for 
example, to poly(.beta.-hydroxyorganoate)s when grown under 
nutrient-limiting conditions. For example, when P. oleovorans is grown 
under nitrogen-limiting conditions on the substrates hexane through 
dodecane, poly(.beta.-hydroxyorganoate)s are formed which, depending on 
the growth substrate used, contain variable amounts of the monomer units. 
In fact, P. oleovorans is capable of producing very unusual 
poly(.beta.-hydroxyorganoate)s, such as those containing relatively long 
n-alkyl pendant groups. By using combinations of feedstocks, e.g., a 
combination of octane and nonane or octanoic and nonanoic acids, 
copolymers can be obtained, e.g., copolymers of .beta.-hydroxyoctanoates 
and .beta.-hydroxynonanoates. Poly(.beta.-hydroxyorganoate)s having 
unsaturated pendant groups have also been produced, for example, from P. 
oleovorans grown with 1-alkenes, 3-hydroxyalkenoic acids, or alkenoic 
acids. 
The PSA compositions of the present invention preferably include a 
poly(.beta.-hydroxyorganoate) in an amount of at least about 20 weight 
percent (wt-%), more preferably in an amount of at least about 30 wt-%. 
Although the compositions of the present invention could include 100 wt-% 
of a poly(.beta.-hydroxyorganoate), preferably there is no greater than 
about 97 wt-% of the a poly(.beta.-hydroxyorganoate). Particularly 
preferred PSA compositions of the present invention include about 40-70 
wt-% poly(.beta.-hydroxyorganoate). 
Suitable poly(.beta.-hydroxyorganoate)s for use in the present invention 
are biodegradable, have a Tg of less than about 10.degree. C., preferably 
less than about 0.degree. C., and more preferably less than about 
-5.degree. C., and are soluble in common organic solvents. The pressure 
sensitive adhesives incorporating these polymers have a Tg of less than 
about 20.degree. C., preferably less than about 5.degree. C., and more 
preferably less than about -5.degree. C. Prior to any crosslinking, 
suitable poly(.beta.-hydroxyorganoate)s have a molecular weight (weight 
average) of at least about 30,000, preferably at least about 50,000, and 
more preferably at least about 100,000. They typically have a molecular 
weight of less than about 2 million. 
These polymers include monomeric units of the general formula: 
##STR3## 
wherein R is an organic group, i.e., aliphatic, alicyclic, or aromatic 
group, containing 1-30 carbon atoms (preferably 1-20 carbon atoms), which 
can be saturated or unsaturated, branched or straight chain group, 
substituted or unsubstituted. The R group can be substituted, i.e., 
functionalized, with Br, Cl, or COOH groups, for example. 
The polymers useful in the PSA compositions of the present invention can 
include more than one type of repeat unit, i.e., monomeric unit, wherein R 
can vary from monomer unit to monomer unit within any one polymer. Thus, 
any one polymer can include a mixture of monomeric units, wherein the side 
chain, i.e., R group, contains anywhere from one carbon to thirty carbons. 
Polymers with good pressure sensitive properties, e.g., little 
crystallization, can tolerate up to a total of about 20 mole-% of 
monomeric units having 1-3 carbon atoms in the side chain. The remainder 
of the monomeric units have 4-30 (preferably 4-20, and more preferably 
4-15) carbon atoms in the side chain. Thus, typical polymers useful in the 
PSA compositions of the present invention can have a total of up to 20 
mole-% monomeric units wherein R is a C.sub.1, C.sub.2, or C.sub.3, group, 
or mixtures thereof, and at least about 80 mole-% monomeric units wherein 
R is a C.sub.4, C.sub.5, C.sub.6, C.sub.7 . . . C.sub.27 group, or 
mixtures thereof. Polymers that contain more than about 20 mole-% 
monomeric units wherein R is a C.sub.1-3 group are generally unacceptable 
pressure sensitive adhesives because such groups tend to crystallize with 
time. Thus, the polymers of the present invention can be homopolymers, 
copolymers, terpolymers, tetrapolymers, etc. There is generally no limit 
to the number of different types of repeat units in any one polymer. 
Examples of poly(.beta.-hydroxyorganoate)s produced by bacteria that are 
useful for the preparation of poly(.beta.-hydroxyorganoate)s include: 
poly(3-hydoxyheptanoate)(R=butyl); 
poly(3-hydroxy-5-methylhexanoate)(R=i-butyl); poly(3-hydroxyoctanoate) 
(R=pentyl); poly(3-hydroxynonanoate) (R=hexyl); poly(3-hydroxydecanoate) 
(R=heptyl); poly(3-hydroxyundecanoate) (R=octyl); 
poly(3-hydroxydodecanoate) (R=nonyl); poly(3-hydroxy-7-octenoate) 
(R=4-pentenyl); poly(3-hydroxy-6-heptenoate) (R=3-butenyl); 
poly(3-hydroxy-8-nonenoate)(R=5-hexenyl); 
poly(3-hydroxyoctanoate-co-3-hydroxynonanoate) (R=pentyl and hexyl, 
respectively);poly(3-hydroxyoctanoate-co-hydroxyundecanoate) (R=pentyl and 
octyl, respectively); poly(3-hydroxy-8-bromooctanoate) (R=5-bromopentyl); 
poly(3-hydroxy-11-bromoundecanoate) (R=8-bromooctyl); 
poly(3-hydroxy-6-bromoheptanoate) (R=4-bromobutyl); 
poly(3-hydroxy-5-phenylvalerate) (R=2-phenylethyl); 
poly(3-hydroxyoctanoate-co-3-hydroxy- 10-undecenoate)(R=pentyl and 
7-octenyl, respectively); 
poly(3-hydroxynonanoate-co-3-hydroxyoctadecanoate) (R=hexyl and 
pentadecyl, respectively); poly(3-nonanoate-co-3-hydroxy-9-octadecenoate) 
(R=hexyl and 6-pentadecenyl, respectively); and 
poly(3-hydroxy-3-phenylbutanoate) (R=benzyl). Each of these polymers is 
identified by its major repeat unit. That is, although each of these 
polymers contains a number of different repeat units, such that they are 
copolymers, terpolymers, etc., they are identified by the repeat units 
having the largest mole percent composition. 
The poly(.beta.-hydroxyorganoate)s of the present invention can be possibly 
either random or block copolymers, depending on the relative reactivities 
of the various monomers. However, they are generally random copolymers, 
particularly because they are generally prepared by bacteria. Typically, 
polymers having a large percentage of two different monomeric units are 
prepared by using two sources of feedstock for the bacteria to convert to 
a polymer. 
A preferred class of polymers of the present invention include unsaturation 
in the side chains (in an uncrosslinked system). Preferably, these 
uncrosslinked polymers have no greater than about 20 mole percent 
monomeric units having unsaturation therein, and more preferably, about 
1-10 mole percent. These monomeric units can have one or more double bonds 
in the sidechains, i.e., R groups. Another preferred class of polymers of 
the present invention include Cl, Br, or COOH groups in the side chain. 
Preferably, these uncrosslinked polymers have no greater than about 20 
mole percent Cl, Br, or COOH groups. 
The addition of one or more tackifiers to the compositions of the present 
invention can provide a PSA having improved tack, lower viscosity, 
improved coatability, and improved peel adhesion. Tackifiers can also 
improve the open time of an adhesive. Compatible tackifiers useful in the 
adhesive compositions of the invention include polar or nonpolar 
tackifiers. Preferably, they include rosin and rosin derivatives, resins 
derived by polymerization of C.sub.5-9 unsaturated hydrocarbon monomers, 
such as polyterpenes and synthetic polyterpenes, and phenol-containing 
resins such as terpene phenolics and pure phenolic resins, and the like. 
As used herein, a "compatible" tackifier is one that is soluble at the 
molecular level in the PSA compositions with no phase separation. 
Hydrocarbon tackifying resins can be prepared by polymerization of monomers 
consisting primarily of olefins and diolefins and include, for example, 
residual by-product monomers of the isoprene manufacturing process. These 
hydrocarbon tackifying resins typically exhibit Ball and Ring Softening 
Points of about 60.degree. C. to about 145.degree. C. Examples of 
commercially available hydrocarbon tackifying resins include, but are not 
limited to terpene polymers, such as polymeric resinous materials obtained 
by polymerization and/or copolymerization of terpene hydrocarbons such as 
the alicyclic, mono, and bicyclic monoterpenes and their mixtures, 
including carene, isomerized pinene, terpinene, terpentene, and various 
other terpenes. 
Commercially available resins of the terpene type include the ZONAREZ 
terpene B-series and 7000 series available from the Arizona Chemical 
Corp., Wayne, N.J. Typical properties reported for the ZONAREZ terpene 
resins include Ball and Ring Softening Points of about 55.degree. C. to 
125.degree. C. (ASTM E28-67), Acid Numbers of less than one (ASTM 
D465-59), and Saponification Numbers of less than one (ASTM D464-59). The 
terpene resin used in the examples below is a poly(.beta.-pinene) resin, 
PICCOLYTE A135 available from Hercules Chemical Co. Inc., which has a Ball 
and Ring Softening Point of 135.degree. C., as well as POLYE 
polyterpene from Hercules. Commercially available aromatic resins include 
WINGTACK+, an aromatic C5 resin, available from Goodyear, Akron, Ohio, and 
INCOPOL H100, a hydrogenated indene, available from Amoco, Chicago, Ill. 
Phenolic modified terpene resins and hydrogenated derivatives thereof are 
also useful tackifiers for the PSA compositions of the present invention. 
For example, the resin product resulting from the condensation, in an 
acidic medium, of a bicyclic terpene and a phenol, as well as pure 
phenolic alkyl resins, are useful tackifiers. Phenolic terpene resins are 
commercially available under the tradename PICOTEX from Hercules 
Corporation, Wilmington, Del. Phenolic resins are commercially available 
from Georgia Pacific, Decatur, Ga., under the designation GP 2103. 
Suitable natural and modified rosins include gum rosin, wood rosin, tall 
oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, and 
polymerized rosin. Rosin esters are particularly useful tackifiers because 
they have generally higher softening points and higher molecular weights 
than unmodified rosins. Ethylene glycol, glycerol, and pentaerythritol are 
the most common alcohols used for modification, e.g., esterification. 
Rosin esters are also quite stable and resistant to hydrolysis. Such 
stability typically increases with the extent of hydrogenation. Rosin 
ester tackifying agents useful in the compositions of the present 
invention have softening temperatures of about 65.degree. C. to about 
110.degree. C. Preferred rosin ester tackifiers are glycerol rosin esters 
commercially available from a variety of sources. For example, glycerol 
rosin esters are available under the tradename FORAL 65, FORAL 85, FORAL 
105, and FORAL AX from Hercules Corp., Wilmington, Del. 
Any combination of tackifiers can be used to improve tack. Preferably, a 
tackifier, or combination of tackifiers, is chosen such that the level of 
tack of the poly(.beta.-hydroxyorganoate)s can be adjusted, depending on 
the application. More preferably, the tackifier is a biodegradable 
tackifier, such as glycerol rosin esters. An amount of a tackifier is used 
effective to adjust the tack of the adhesive for the application desired. 
Preferably, the total amount of tackifier(s) in the compositions of the 
present invention is less than about 400 parts, more preferably 3-250 
parts, and most preferably 11-150 parts, by weight per 100 parts of 
polymer. In corresponding weight percentages, the total amount of 
tackifier(s) in the compositions of the present invention is preferably 
less than about 80 wt-%, more preferably in a range of about 3-71 wt-%, 
and most preferably 10-60 wt-%. 
The PSA films of the present invention can be crosslinked to improve the 
internal strength of the adhesive. For example, the shear adhesion of a 
tackified composition can be enhanced by crosslinking with no loss of peel 
adhesion. They can be crosslinked by radiation, e.g., e-beam, with or 
without a crosslinking agent. For example, without the presence of a 
crosslinking agent, e.g., crosslinker, sensitizer, or photoinitiator, 
radicals can be generated in the polymer that can then crosslink. 
Alternatively, a crosslinking agent can be added to assist in crosslinking 
and/or become incorporated into the crosslinked polymer. Crosslinking 
agents that do not require radiation activation can also be used, such as 
certain chemical crosslinkers. Thus, suitable crosslinking agents can be 
chemical crosslinkers, either organic or inorganic crosslinkers, or 
radiation active crosslinkers. Other crosslinking agents include thermal 
initiators, photoinitiators, and sensitizers. If desired, a crosslinking 
agent is used in an amount effective to cause crosslinking and improve the 
internal strength of the adhesive. It should be understood that a mixture 
of crosslinking agents can be used to advantage, such as a photoinitiator 
and a sensitizer. 
Suitable thermal initiators include, but are not limited to, peroxides such 
as benzoyl peroxide, dibenzoyl peroxide, cumyl peroxide, di-t-butyl 
peroxide, methyl ethyl keto peroxide, and nitriles such as 
azobisisobutyronitrile. Certain of these thermal initiators are also 
chemical crosslinkers. Preferably, a thermal initiator, or mixture of 
thermal initiators, (or chemical crosslinker) can be present in the PSA 
compositions in an amount of about 0.05-11 parts, more preferably about 
0.1-5.3 parts, and most preferably about 0.1-3.1 parts, by weight of 100 
parts of the polymer. In corresponding weight percentages (based on the 
total weight of the composition), the total amount of thermal initiator(s) 
in the compositions of the present invention is preferably in a range of 
about 0.05-10 wt-%, more preferably about 0.1-5.0 wt-%, and most 
preferably about 0.1-3.0 wt-%. 
Suitable photoinitiators include, but are not limited to: aldehydes, such 
as benzaldehyde, acetaldehyde, and their substituted derivatives; ketones 
such as acetophenone, benzophenone, bisbenzophenone, polybenzophenone, and 
their substituted derivatives such as SANDORAY 1000 (Sandoz Chemicals, 
Inc., Charlotte, N.C.); quinones photoinitiator such as the benzoquinones, 
anthraquinone and their substituted derivatives; thioxanthones such as 
2-isopropylthioxanthone and 2-dodecylthioxanthone; and certain 
chromophore-substituted vinyl halomethyl-symtriazines such as 
2,4-bis(trichloromethyl)-6-(3',4'-dimethoxyphenyl)-sym-triazine. Certain 
of these photoinitiators are also radiation crosslinkers, such as 
bisbenzophenone and triazines. Preferably, a photoinitiator, or mixture of 
photoinitiators, (or alternatively, radiation active crosslinker(s)) can 
be present in the PSA compositions in an amount of about 0.05-11 parts, 
more preferably about 0.1-5.3 parts, and most preferably about 0.1-3.1 
parts, by weight of 100 parts of the polymer. In corresponding weight 
percentages (based on the total weight of the composition), the total 
amount of photoinitiator(s) in the compositions of the present invention 
is preferably in a range of about 0.05-10 wt-%, more preferably about 
0.1-5.0 wt-%, and most preferably about 0.1-3.0 wt-%. 
Suitable sensitizers include, but are not limited to, xanthone, 
acetophenone, benzaldehyde, o-dibenzoylbenzenc, benzophenone, 
2-acetylfluorenone anthraquinone, flavone, Micheler's ketone, 
4-acetylbiphenyl, .beta.-naphthyl phenyl ketone, .beta.-naphthaldehyde, 
.beta.-acetonaphthone, .alpha.-acetonaphthone, .alpha.-naphthaldehyde, 
biacetyle, benzil, flurorenone, and duroquinone. Preferably, a sensitizer, 
or mixture of sensitizers, can be present in the PSA compositions in an 
amount of about 0.05-11 parts, more preferably about 0.1-5.3 parts, and 
most preferably about 0.1-3.1 parts, by weight of 100 parts of the 
polymer. In corresponding weight percentages (based on the total weight of 
the composition), the total amount of sensitizer(s) in the compositions of 
the present invention is preferably in a range of about 0.05-10 wt-%, more 
preferably about 0.1-5.0 wt- %, and most preferably about 0.1-3.0 wt-%. 
The adhesive compositions containing radiation crosslinkers, 
photoinitiators, and sensitizers, can be cured using a source of radiation 
of sufficient energy (i.e., wavelength range) to generate free radicals 
when incident upon the particular crosslinking agent selected for use in 
the composition. The preferable wavelength range for the crosslinking 
agents disclosed above is about 400-250 nm. The radiant energy in this 
preferred range of wavelengths required to crosslink the adhesive film of 
the invention is about 50-5000 milliJoules/cm.sup.2 and more preferably 
about 100-1000 milliJoules/cm.sup.2. 
Crosslinked adhesive films prepared from the PSA compositions of the 
present invention preferably have a percent gel in the range of about 2-95 
weight percent, more preferably about 30-80 weight percent, and most 
preferably about 50-70 weight percent. As used herein, the percent gel is 
corrected for soluble tackifying resins and other additives as hereinafter 
described. 
Minor amounts, i.e., less than about 50 wt-%, of additives can also be 
included in the composition to provide adhesives for particular advantage 
and for special end uses. Such additives may include pigments, dyes, 
fillers, stabilizers, ultraviolet absorbers, antioxidants, processing 
oils, and the like. Antioxidants can be used to stabilize static shear, 
for example. Plasticizers can also be used, however, they are not 
particularly desirable-because they tend to reduce the internal strength 
of the adhesive. Preferred additives are those that are degradable. 
Preferably, the amount of additives used can vary from 0. 1 to 50 weight 
percent depending on the end use desired. 
The adhesive compositions of the present invention are easily coated on 
suitable flexible or inflexible backing materials, preferably flexible 
backing materials, by conventional coating techniques to produce coated 
adhesive sheet materials in accord with the present invention. The 
flexible backing material can be any material conventionally utilized as a 
tape backing, as well as other flexible materials. Examples of substrate 
materials, i.e., backing materials, include, but are not limited to: 
polymer films such as polyester (e.g., polyethylene terephthalate), 
polypropylene (e.g., biaxially oriented polypropylene), polyethylene, 
polyvinyl chloride, polyurethane, cellulose acetate, and ethyl cellulose; 
woven and nonwoven fabrics formed of threads or fibers of synthetic or 
natural materials such as cotton, nylon, rayon, glass, or ceramic 
material; metals and metal foils such as aluminum, copper, lead, gold and 
the like; paper; glass; ceramics; and composite materials comprised of 
laminates of one or more of these materials. Preferably, the adhesive 
composition can be coated on degradable substrates such as degradable 
plastic films, paper, and woven or nonwoven fabrics made of degradable 
threads or fibers. 
The PSA compositions of the present invention can be coated from solution 
by any of the coating processes well known in the art, such as knife 
coating, roll coating, gravure coating, curtain coating, spray coating, 
etc. Furthermore, the PSA compositions of the invention can be applied by 
extrusion coating, coextrusion coating, thermal coating, and the like, 
with no solvent present, thereby eliminating environmental and toxicity 
problems associated with solution coating processes. Useful coating 
thicknesses for the present invention are in the range of about 12-2500 
.mu.m, preferably in the range of about 25-250 .mu.m, and more preferably, 
in the range of about 25-125 .mu.m. 
Another embodiment of the invention comprises a laminated structure of at 
least a first and a second substrate, the substrates being joined by a 
layer of the adhesive composition of the invention. At least one of the 
substrates is capable of transmitting radiation so that the adhesive film 
can be crosslinked. 
Objects and advantages of this invention are further illustrated by the 
following examples. The particular materials and amounts thereof recited 
in these examples as well as other conditions and details, should not be 
construed to unduly limit this invention. All materials are commercially 
available except where stated or otherwise made apparent. 
EXAMPLES 
The following nonlimiting examples include exemplary preparations of the 
adhesives of the invention. All parts, percentages, ratios, etc., herein 
and in the rest of the specification are by weight unless otherwise 
specified. 
Preparation and Characterization of Poly(.beta.-Hydroxyorganoate)s 
The polymers used in the PSA compositions of the present invention can be 
prepared according to the procedures described in K, Fritzsche et al., 
Int. J. Biol. Macromol, 12 85-91 (1990); H. Brandl et al., Applied 
Environ. Microbiol., 54 1977-1982 (1988); R. W. Lenz et at., FEMS 
Microbiology Reviews, 103, 207-214 (1992); R. A. Gross et al., 
Macromolecules, 22, 1106-1115 (1989); B. Hazer et al., Macromolecules, 27, 
45-49 (1994); R. Peres et at., Polymer, 35, 1059-1067 (1994); K. Fritzsche 
et at., Makromol. Chem., 191, 1957-1965 (1990); and U.S. application Ser. 
No. 07/939,248, filed on Sep. 2, 1992, entitled "Production of 
Polyhydroxyalkanoates from Pseudomonas." 
Bacterial strain 
The organism used was Pseudomonas oleovorans (ATCC 29347). Stock cultures 
were stored on agar plates at 4.degree. C. Medium composition, stock 
culture, and inoculum preparation are described in detail in T. L. Bluhm 
et al., Macromolecules, 19, 2871-2876 (1986). 
Growth Condition 
The experiments were carried out with a growth medium containing the 
following materials: (NH.sub.4).sub.2 HPO.sub.4, 45 mM; K.sub.2 HPO.sub.4, 
33 mM; KH.sub.2 PO.sub.4, 27 mM; and MgSO.sub.4, 2.5 mM. A microelement 
solution was added (0.1% v/v) which contained the following (per liter of 
1N HCl): 2.78 g FeSO.sub.4.7H.sub.2 O; 1.98 g MnCl.sub.2.4H.sub.2 O; 2.81 
g CoSO.sub.4.7H.sub.2 O; 1.67 g CaCl.sub.2.2H.sub.2 O; 0.17 g 
CuCl.sub.2.2H.sub.2 O; 0.29 g ZnSO.sub.4.7H.sub.2 O. 
The medium was supplemented with 25 mM sodium octanoate for the preparation 
of poly(.beta.-hydroxyoctanoate) ("PHO"); 40 mM sodium nonanoate for the 
preparation of poly(.beta.-hydroxynonanonoate) ("PHN"); 25 mM total 
mixture of a 9:1 molar ratio of sodium octanoate and sodium undecanoate 
for the preparation of poly(.beta.-hydroxyoctanoate-co-.beta.-hydroxy- 
11-undecenoate)("PHO/U"), 15 mM each of sodium octanoate and sodium 
nonanoate for the preparation of 
poly(.beta.-hydroxyoctanoate-co-.beta.-hydroxynonanoate) ("PHO/N"). The pH 
was adjusted to 7.0. These sodium salt feedstocks were prepared in situ 
from NaOH and the corresponding acid. 
Shake flask cultures were cultivated in 500 mL Erlenmeyer flasks, 
containing 200 mL of medium at 30.degree. C. and 150 rpm (revolutions per 
minute). Modified flasks were indented to improve the aeration of the 
culture during shaking. Fermentor cultures were cultivated in a 2-liter 
Biostat E bioreactor (B. Braun Biotech Inc., Allentown, Pa.) The culture 
volume was 1.0 L; the temperature was maintained at 30.degree. C. and pH 
at 7.0; stirring was carried out at 250 rpm; and the aeration rate was 2.0 
L of air per minute. Larger fed batch cultures were grown in Microferm 114 
fermentors (New Brunswick Scientific, Edison, N.J.) using culture volumes 
of 12 L; aeration was at 5 L/minute; stirring was carried out at 250-300 
rpm; and temperature and pH were maintained at 30.degree. C. and 7.0, 
respectively. Feedstock (120 mL), consisting of 1.0M sodium octanoate (or 
other sodium salt of an organic acid), and 125 mM mM NH.sub.4.sup.+ growth 
media (final culture concentration of 10 mM and 2.5 mM NH.sub.4.sup.+ 
respectively) were added after 10 hours growth, and at 2 hour intervals 
thereafter. For other salts of organic acid feedstocks, the addition was 
such as to maintain growth. Cultures were harvested after 18 hours. 
Harvest times for other polymers were: 72 hours for PHN; 22 hours for 
PHO/N; 24 hours for PHO/U. Dissolved oxygen was measured using a 
polarographic electrode (obtained from Ingold Inc., Wilmington, Mass.). 
Oxygen consumption of the culture was determined by analyzing the oxygen 
concentration in the air inlet and outlet of the bioreactor using an OM-14 
oxygen analyzer (Beckman Inc., Wakefield, Mass.). These parameters yielded 
a maximum oxygen transfer rate of 250 mL L.sup.-1 h.sup.-1. In continuous 
cultures, growth rates were established by increasing the cell density, 
and adjusting the dilution rate to maintain a given cell density. Aeration 
was constant at 2.0 liter of air per minute. All continuous culture 
experiments were done using the Biostat E bioreactor. 
Cell growth was determined photometrically by measuring the optical density 
(O.D.) of the culture at 660 nm, gravimetrically by weighing the amount of 
dry cells after washing and lyophilization and also by plate counting 
methods. Cells were harvested by centrifugation (4.degree. C., 
12000.times. g, 15 minutes) resuspended in distilled water, and 
repelleted. Plate counting was done using stock culture media with 2% agar 
added, incubated overnight at 30.degree. C. and counted. Only those plates 
with between 20 and 100 colonies were counted. 
Poly(.beta.-hydroxyorganoate) Ouantification and Analysis 
To determine the polymer content and composition of lyophilized whole cells 
the intracellular poly(.beta.-hydroxyorganoate) was degraded to its 
constituent hydroxycarboxylic acid methyl esters by methanolysis. The 
methyl esters were then assayed by gas chromotography according to the 
method described in H. Brandl et at., Appl. Environ. Microbiol., 54, 
1977-1982 (1988), the description of which is incorporated herein by 
reference. 
Extraction of the Polymer 
Poly(.beta.-hydroxyorganoate) was extracted from lyophilized cells into 
chloroform using a soxhlet extractor, precipitated in 10 volumes of 
methanol, centrifuged, and allowed to dry to constant weight according to 
the procedure outlined in H. Brandi et al., Appl. Environ, Microbiol, 54, 
1977-1982 (1988), the description of which is incorporated herein by 
reference. 
Molecular Weight Determination 
The molecular weight of the extracted polymer was determined by gel 
permeation chromatography. Chloroform was used as the eluent at a flow 
rate of 1.0 mL/minute. Polymer samples were dissolved in chloroform (20 
mg/mL) and 100 microliters of this solution was analyzed. Calibration 
curves were generated using polystyrene standards. The M.sub.w (weight 
average molecular weight), M.sub.n (number average molecular weight), and 
PDI (polydispersity index) are reported. 
PHO Analysis 
Molecular weight determination was done by Gel Permeation Chromatography in 
chloroform solvent using polystyrene standards. Repeat unit analysis was 
done using Gas Chromatography. The poly(.beta.-hydroxyorganoate) undergoes 
methanolysis, and the 3-hydroxy methyl esters of the hydrolyzed acid 
repeat units were analyzed. 
______________________________________ 
Gas Chromatography 
SIDE CHAIN 
LENGTH REPEAT UNIT MOLE % 
______________________________________ 
C-3 C-6 12 
C-5 C-8 88 
______________________________________ 
Thermal Analysis 
T.sub.g =-36.degree. C. 
T.sub.m =56.degree. C. 
.DELTA.H.sub.m =24.0 J/g 
Molecular Weight Determination 
M.sub.w =210,000 
M.sub.n =94,000 
PDI=2.2 
PHN Analysis 
Molecular weight determination was done by Gel Permeation Chromatography in 
chloroform solvent using polystyrene standards. Repeat unit analysis was 
done using Gas Chromatography. The poly(.beta.-hydroxyorganoate) undergoes 
methanolysis, and the 3-hydroxy methyl esters of the hydrolyzed acid 
repeat units are analyzed. 
______________________________________ 
Gas Chromatography 
SIDE CHAIN 
LENGTH REPEAT UNIT MOLE % 
______________________________________ 
C-2 C-5 4.6 
C-4 C-7 42.6 
C-6 C-9 52.9 
______________________________________ 
Thermal Analysis 
T.sub.g =-34.degree. C. 
T.sub.m =49.degree. C. 
.DELTA.H.sub.m =24.3 J/g 
Molecular Weight Determination 
M.sub.w =143,000 
M.sub.n =57,100 
PDI=2.5 
PHO/N Analysis 
The PHO/N polymer was analyzed using GC, DSC, and GPC methodology. Analyses 
were done to determine the repeat unit composition, melting and glass 
transition temperatures, and the molecular weight of the samples. 
Molecular weight was determined by GPC using polystyrene standards. The 
results of these analyses are tabulated below. 
______________________________________ 
Gas Chromatography 
SIDE CHAIN 
LENGTH REPEAT UNIT MOLE % 
______________________________________ 
C-3 C-6 3.6 
C-4 C-7 12.7 
C-5 C-8 37.4 
C-6 C-9 21.6 
C-7 C-10 0.7 
C-8 C-11 12.9 
C-9 C-12 11.0 
______________________________________ 
Thermal Analysis 
T.sub.g =-32.2.degree. C. 
T.sub.m =56.9.degree. C. 
.DELTA.H.sub.m =15.0 J/g 
Molecular Weight Determination 
M.sub.w =209,000 
M.sub.n =69,000 
PDI=3.03 
PHO/U[1] Analysis 
The PHO/U[1] polymer was analyzed using GPC, NMR, and DSC methodology. 
Analyses were done to determine, melting and glass transition temperatures 
and the molecular weight of the samples. Molecular weight was determined 
by GPC using polystyrene standards. The results of these analyses are 
tabulated below. 
Thermal Analysis 
T.sub.g =-34.degree. C. 
T.sub.m =59.degree. C. 
.DELTA.H.sub.m =22.0 J/g 
Molecular Weight Determination 
M.sub.w =165,000 
M.sub.n =62,000 
PDI=2.7 
Proton NMR Analysis Analysis of the proton NMR of the sample indicated that 
there is 7-9% unsaturated repeat units in the polymer. 
PHO/U[2] Analysis 
The PHO/U[2] polymer was analyzed using GPC, NMR, and DSC methodology. 
Molecular weight was determined by GPC using polystyrene standards. The 
results of these analyses are tabulated below. 
Thermal Analysis 
T.sub.m =46.6.degree. C. 
.DELTA.H.sub.m =3.4 J/g 
Molecular Weight Determination 
M.sub.w =164,000 
M.sub.n =62,000 
PDI=2.60 
Proton NMR Analysis Analysis of the proton NMR of the sample indicated 
thatthere is 12-16 % unsaturated repeat units in the polymer. 
Test Methods 
The test procedures used in the examples to evaluate and compare the 
properties of the PSA compositions and tapes made from them are industry 
standard tests. These tests are described in detail in various 
publications of the American Society for Testing Materials (ASTM), 
Philadelphia, Pa. and the Pressure Sensitive Tape Council (PSTC), Glenview 
Ill. References to these standards are also given. 
Shear Strength (ASTM D-3654-78) 
The shear strength is a measure of the cohesiveness or internal strength of 
an adhesive. It is based upon the amount of force required to pull an 
adhesive strip from a standard flat surface in a direction parallel to the 
surface to which it has been affixed with a definite pressure. It is 
measured in units of time (minutes) required to pull a standard area of 
PSA coated sheet material from a stainless steel test panel under stress 
of a constant, standard load. 
The tests were conducted on adhesive coated strips applied to a stainless 
steel panel such that a 12.7 mm by 12.7 mm portion of each strip was in 
firm contact with the panel, with one end portion of the tape being free. 
The panel with coated strip attached was held in a rack such that the 
coated surface of the panel formed an angle of 182.degree. with the 
vertical tape free end, which was then tensioned by application of a force 
of one kilogram applied as a hanging weight from the free end of the 
coated strip. The 2.degree. greater than 180.degree. was used to negate 
peel adhesions, thus insuring that only the shear forces were measured in 
order to more accurately determine the holding power of the tape being 
tested. The time elapsed for each test specimen to separate from the steel 
panel was recorded as the shear strength. 
Mode Of Failure (MOF) 
The time at which the mass falls is called "Shear Test" and is reported as 
"10,000+" if the tape has not failed after 10,000 minutes. With each Shear 
is indicated the mode of failure as follows: 
PO=pop-off, i.e.,75-100% adhesive failure from steel plate; 
CF=adhesive split: both surfaces completely covered by adhesive; 
NTR=residue failure: adhesive covering 100% of backing with a small residue 
transferred to panel; 
The pop-off failure mode is preferred because it is indicative of adhesive 
failure of the adhesive/steel interfacial bond as opposed to cohesive 
failure of the adhesive. Adhesives of various shear adhesions, all within 
the range of the present invention (1-10,000+ minutes), are preferred 
depending on end-use applications. Two specimens of each tape were tested 
and the shear tests were averaged to obtain the shear value. 
Peel Adhesion (ASTM D 3330-76) 
The peel adhesion is the force required to remove a PSA coated test 
specimen from a test panel measured at a specific angle and rate of 
removal. In the examples, this force was expressed in Newtons per 
decimeter (N/din) width of coated sheet. The procedure followed was: 
1) A test specimen 12.7 mm wide was applied to a horizontally 
positioned clean glass test plate. A 2.2 kg rubber roller was used to press 
a 12.7 cm length of specimen into firm contact with the glass surface. 
2) The free end of the specimen was doubled back nearly touching itself so 
the angle of removal was 180.degree.. The free end was attached to the 
adhesion tester scale. 
3) The glass test plate was clamped in the jaws of tensile testing machine, 
which was capable of moving the plate away from the scale at a constant 
rate of 2.3 meters per minute. 
4) The scale reading in Newtons was recorded as the tape was peeled from 
the glass surface. 
Percent Gel Test (ASTM D 3616-82) 
The percent gel is used as an indication of cure level. The percent gel is 
100 times the gelled mass divided by the total mass of material that is 
capable of forming a gelled network. 
Crosslinking improves the creep and shear resistance of pressure-sensitive 
adhesives. The transition from a cohesive to an adhesive failure during 
peeling advances to a lower peel rate and higher temperature with an 
increase in crosslink density. 
Many important properties of crosslinked pressure-sensitive adhesives vary 
with the gel content. Hence, determination of the gel content provides a 
means for controlling the process and thereby raising the quality of the 
tape. 
Extraction tests permit verification of the proper gel content of polymers 
in the PSAs and they also permit comparison between different crosslinked 
adhesives and their specific end uses. 
Gel Content Determination: 
A square test specimen (3.81 cm.times.3.81 cm) containing approximately 
0.15 g of PSA was cut from the tape and placed in a 120-mesh stainless 
steel basket measuring approximately 4.times.8 cm. The contents were 
weighed to the nearest 0.1 mg and then immersed in a capped beaker 
containing sufficient toluene to cover the specimen. After extraction for 
48 hours, the basket (containing the specimen) was removed, drained, and 
placed in an oven at 93.degree. C. The basket and specimen were dried to a 
constant weight and the gel content was determined as follows: 
##EQU1## 
Two specimens of each tape were tested and the results were averaged to 
obtain the gel content value. 
Biodegradability Test for Poly(hydroxyorganoate) Adhesives in the Presence 
of Ps. Maculicola 
Ps. Maculicola (previously ATCC 11781) was obtained from the Department of 
Microbiology, University of Massachusetts Amherst, Amherst, MA. The 
organism was cultured on E* media agar plates with the addition of 20 mM 
glucose at 37.degree. C. for 48 hours. E* media agar plates were prepared 
from the following recipe: 5.94 g of (NH.sub.4).sub.2 HPO.sub.4 ; 5.8 g of 
K.sub.3 PO.sub.4 ; and 3.7 g of KH.sub.2 PO.sub.4. The above dry mix was 
added to 1.0 L of water containing 15.0 g of granular agar. The media was 
supplemented with the following trace elements: 20 mL of 100 mM MgSO.sub.4 
; and 1.0 mL of the micro-elements solution (1.0 L of 1.0M HCl containing: 
2.78 g FeSO.sub.4 7H.sub.2 O; 1.98 g of MnCl.sub.2.4H.sub.2 O; 2.81 g of 
CoSO.sub.4 7H.sub.2 O; 1.67 g of CaCl.sub.2.2H.sub.2 O; 0.17 g of 
CuCl.sub.2.2H.sub.2 O; and 0.29 g of ZnSO.sub.4.7H.sub.2 O. 
An inoculum suspension was prepared in E* media broth using a 48 hour 
culture of the Ps. Maculicola to a density of a 0.5 McFarland Turbidity 
Standard #1 (approximately 10.sup.8 organisms per mL). 
The adhesive samples were cut into 1.25.times.1.25 or 1.25.times.0.7 cm 
pieces and were attached to the bottom of sterile polystyrene dishes 
(100.times.25 mm) with epoxy (either a DEV-TUBE 5-minute epoxy from 
Devcon, Illinois Tool Works, Danvers, Mass., or an extra fast setting 
epoxy from Hardman, Inc., Belleville, N.J.) with the test adhesive 
exposed. The epoxy was allowed to cure for at least 2 weeks at room 
temperature. To each petri dish was added 50 mL of E* media broth 
containing 10 mM glucose. The inoculum (50 .mu.l) was added to each petri 
dish and the samples were incubated at 28.degree. C. for various time 
periods. Two sets of samples were prepared. In the first set, the inoculum 
and nutrient broth solutions were replaced at 14 days. In the second set, 
the same suspension was used for the duration of the test. At 7, 14, 21, 
and 28 days, sample sets were removed from the incubator, rinsed with 
deionized water, and allowed to dry. 
The adhesive samples were then visualized using scanning electron 
microscopy to determine if bacterial attachment to the surface had 
occurred and if etching or erosion of the surface had occurred. 
EXAMPLE 1 
An Adhesive Containing Poly(hydroxynonanoate) [PHN] 
A laboratory scale coating was prepared by allowing 4 g of 
poly(.beta.-hydroxynonanoate) (prepared as described above) to dissolve in 
8 g of chloroform. This solution was knife-coated onto a 2 mil (50 .mu.m) 
PET backing (Minnesota Mining and Manufacturing, St. Paul, Minn.) using a 
handspread coater. The handspread was dried at room temperature for 12 
hours to remove the chloroform and the dry coating thickness was 23 .mu.m. 
The sample was cut for use in the test procedures described for peel 
adhesion and shear strength and the results are shown in Table 1. 
EXAMPLE 2 
An Adhesive Containing a UV-cured PHN 
The laboratory scale coating of Example 2 was prepared in the same manner 
as that in Example 1, except that to the chloroform solution was added 12 
mg of IRGACURE 184 (Ciba Geigy, Chicago, Ill.). The coating thickness was 
20 .mu.m. The handspread was subjected to UV (15 W black lights, 1 hour at 
a distance of 10 cm) radiation after drying to effect a degree of 
crosslinking. The peel and shear test results for this material are shown 
in Table 1. 
EXAMPLE 3 
A Tackified Adhesive Containing PHN 
The laboratory scale coating of Example 3 was prepared in the same manner 
as that in Example 1, except that 2.67 g of polymer was used, and to the 
chloroform solution was added 1.33 g of FORAL 85 hydrogenated rosin ester 
(Hercules Chemical, Wilmington, Del.). The coating thickness was 20 .mu.m. 
The peel and shear test results for this material are shown in Table 1. 
EXAMPLE 4 
A Tackified UV-cured Adhesive Containing PHN 
The laboratory scale coating of Example 4 was prepared in the same manner 
as that described in Example 2, except that 2.67 g of polymer was used, 
and to the chloroform solution was added 1.33 g of FORAL 85 hydrogenated 
rosin ester. The coating thickness was 28 .mu.m. The peel and shear test 
results are shown in Table 1. 
EXAMPLE 5 
A UV-cured PHN Adhesive with Tackifier Resin 
The laboratory scale coating of Example 5 was prepared in the same manner 
as that described in Example 4, except that to 0.40 g of 
poly(.beta.-hydroxynonanoate), 0.20 g of FORAL 85 and 6 mg of benzophenone 
(Aldrich Chemical Co., Milwaukee, Wis.) were added 1.33 g of chloroform. 
The dry coating thickness was 25 .mu.m. The peel and shear tests for this 
UV-cured tape are shown in Table 1. 
EXAMPLES 6-31 
Examples 6-31 were prepared as described in Example 5, except that the 
ratio PHN:tackifier:photoinitiator ratio was varied for different types 
and concentrations of tackifying resins and different types and 
concentrations of crosslinking agent. The compositional information and 
the coating thickness are shown in Table 1. The results of the peel and 
shear tests for these UV-cured tapes are shown in Table 1. 
EXAMPLES 32-37 
An Adhesive Containing poly(.beta.-hydroxyoctanoate) [PHO] 
Examples 32-37 were prepared as described in Example 5, except that the 
polymer used was poly(.beta.-hydroxyoctanoate) (prepared as described 
above) and different types and concentrations of tackifying resins and 
crosslinking agents were used. The data describing the peel and shear test 
results are shown in Table 2. 
EXAMPLE 38 
An Adhesive Containing 
Poly(.beta.-hydroxyoctanoate-co-.beta.-hydroxynonanoate) [PHO/N] 
A laboratory scale coating was prepared by allowing 0.4 g of 
poly(.beta.-hydroxyoctanoate-co-.beta.-hydroxynonanoate) (prepared as 
described above) to dissolve in 0.8 g of chloroform. This solution was 
knife-coated onto a 2 mil (50 .mu.m) PET backing (Minnesota Mining and 
Manufacturing, St. Paul, Minn.) using a handspread coater. The handspread 
was dried at room temperature for 12 hours to remove the chloroform. The 
dry coating thickness was 25 .mu.m. The sample was cut for use in the test 
procedures described for peel adhesion and shear strength. The results are 
shown in Table 3. The material of Example 38 was subjected to the 
Biodegradability Test described above. The results of the test are shown 
in Figures 2 and 3, which are Scanning Electron Micrographs of the sample 
after 28 days exposure, with and without replacing the inoculum and 
nutrient broth solutions at 14 days, respectively. For reference, a 
micrograph of the initial sample is included as FIG. 1. 
FIG. 1 shows a smooth surface of the sample as coated from solution. The 
surface shown in FIG. 2 has been eroded by the action of the 
microorganisms, i.e., biodegradation. The extent of biodegradation was 
greater when the inoculum and nutrient broth solutions were replaced at 14 
days as shown in comparing FIG. 2 (replaced) and FIG. 3 (not replaced). 
EXAMPLES 39-65 
Adhesive tapes containing PHO/N were prepared as described in Example 38, 
except to 0.4 g of PHO/N was added 0.20 g of a tackifier resin and an 
amount of crosslinking agent as described in Table 3. Different types and 
concentrations of tackifying resins and crosslinking agents. The data 
describing the peel and shear test results are shown in Table 3. A larger 
quantity sample of Example 41 was prepared in the same manner in order to 
provide samples for the Biodegradability Test. The results in the 
biodegradability test on Example 41 are shown in FIGS. 5 and 6, which are 
Scanning Electron Micrographs of the sample at 28 days exposure, with and 
without replacing the inoculum and nutrient broth solutions at 14 days, 
respectively. For reference, a micrograph of the initial sample is 
included as FIG. 4. 
FIG. 4 shows the surface of Example 41 as coated from solution. The surface 
shown in FIG. 5 has been eroded by the action of the microorganisms, i.e., 
biodegradation, after 28 days in the Biodegradability Test. The extent of 
biodegradation was greater when the inoculum and the nutrient broth 
solutions were replaced at 14 days, as can be seen in comparing FIG. 5 
(replaced) and FIG. 6 (not replaced). 
EXAMPLE 66 
An Adhesive Containing 
Poly(.beta.-hydroxyoctanoate-co-.beta.-hydroxy-10-undecenoate) [PHO/U] 
A laboratory scale coating was prepared by allowing 0.4 g of 
poly(.beta.-hydroxyoctanoate-co-.beta.-hydroxyundecenoate) (prepared as 
described above) to dissolve in 0.8 g of chloroform. This solution was 
knife-coated onto a 2 mil (50 .mu.m) PET backing (Minnesota Mining and 
Manufacturing, St. Paul, Minn.) using a handspread coater. The handspread 
was dried at room temperature for 12 hours to remove the chloroform. The 
dry coating thickness was 20 .mu.m. The sample was cut for use in the test 
procedures described for peel adhesion and shear strength. The results are 
shown in Table 4. 
EXAMPLES 67-90 
Adhesive tapes containing PHO/U were prepared as described in Example 66, 
except to 0.4 g of PHO/U was added 0.20 g of a tackifier resin and an 
amount of crosslinking agent as described in Table 3. PHO/U of two 
different compositions was used in the preparation of the adhesives. The 
difference is noted in Table 4. PHO/U[1] contains 7-9 mole-% unsaturated 
side chains and PHO/U[2] contains 12-16 mole-% unsaturated side chains. 
Different types and concentrations of tackifying resins and crosslinking 
agents were used. The data describing the peel and shear test results are 
shown in Table 4. 
EXAMPLES 91-96 
Preparation of UV cured Adhesives for use in the % Gel Test 
Examples 91-96 were prepared as described in Example 2, except that either 
PHN or PHO/U was used as the polymer and various amounts of the 
photoinitiator, benzophenone (Aldrich Chemical Co., Milwaukee, Wis.), was 
used. The compositional information and the results of the % Gel Test are 
described in Table 5. 
TABLE 1 
__________________________________________________________________________ 
Coating wt Static 
thickness 
180.degree. peel (glass) 
shear 
MOF in 
Ex # 
Composition (.mu.m) 
(N/dm) (min) 
shear 
__________________________________________________________________________ 
1 PHN 23 1 13 PO 
2 PHN, 0.3% IRGACURE 184 20 1 14 PO 
3 PHN, 35% FORAL 85 20 81 [AT] 1 CF 
4 PHN, 35% FORAL 85, 0.3% IRGACURE 184 
23 82 [AT] 1 CF 
5 PHN, 35% FORAL 85, 1% Bzophn 
28 79 [CF] 2 CF 
6 PHN, 35% FORAL 85, 9% Bzophn 
20 28 s 2 CF 
7 PHN, 35% FORAL AX, 1% Bzophn 
28 66 [CF] 1 CF 
8 PHN, 30% FORAL AX, 10% Bzophn 
28 85 [CF] 2 CF 
9 PHN, 35% FORAL AX, 0.15% MPBT 
25 50 [CF] 1 CF 
10 PHN, 35% PICCOLYTE A135, 1% Bzophn 
20 29 s 167 CF 
11 PHN, 30% PICCOLYTE A135, 10% Bzophn 
25 106 [CF] 
1128 CF 
12 PHN, 32% PICCOLYTE A135, 5% Bzophn 
25 33 s, [CF] 
1133 CF 
13 PHN, 35% PICCOLYTE A135, 0.15% MPBT 
25 74 36 CF 
14 PHN, 35% REGALRITE 355, 1% Bzophn 
25 69 2 CF 
15 PHN, 30% REGALRITE 355, 10% Bzophn 
25 87 [PO] 6 CF 
16 PHN, 35% REGALRITE 355, 0.15% MPBT 
23 i 19 3 CF 
17 PHN, 35% GP 2103, 1% Bzophn 
23 136 s, [CF] 
11 CF 
18 PHN, 30% GP 2103, 10% Bzophn 
23 93 [CF] 1 CF 
19 PHN, 35% GP 2013, 0.15% MPBT 
23 92 20 CF 
20 PHN, 30% POLYE, 10% Bzophn 
25 83 [PO/CF] 
2 CF 
21 PHN, 35% POLYE, 0.15% MPBT 
25 si 59 5 CF 
22 PHN, 30% EASTOTAC H100R, 10% Bzophn 
25 i 4 [PO] 10,000+ 
23 PHN, 30% INDOPOL H100, 10% Bzophn 
28 si 13 [PO/NTR] 
1 PO 
24 PHN, 30% PICOTEX LC, 10% Bzophn 
33 68 s, [CF] 
2754 PO 
25 PHN, 32% PICOTEX LC, 5% Bzophn 
25 97 [CF] 1171 PO 
26 PHN, 33% PICOTEX LC, 1% Bzophn 
25 76 [CF] 2 CF 
27 PHN, 30% WINGTACK+, 10% Bzophn 
25 si 23 [PO] 765 PO 
28 PHN, 32% WINGTACK+, 5% Bzophn 
25 i 12 [PO] -- 
29 PHN, 33% WINGTACK+, 1% Bzophn 
23 i 18 [PO1 -- 
30 PHN, 32% PICCOLYTE A135, 5% Bzophn 
25 51 s, [CF] 
5257 CF 
31 PHN, 32% PICOTEX LC, Bzophn 
25 111 [CF] 
475 CF 
__________________________________________________________________________ 
Abbreviations: s = raspy peel, si = slightly immiscible, i = immiscible, 
PO = pop off, AT = adhesive transfer, CF = cohesive failure, NTR = 
nontacky residue, Bzophn = benzophenone, MPBT = 
2,4bis(trichloromethyl)-6-(3methoxyphenyl)-sym-triazine (manufactured by 
Minnesota Mining and Manufacturing Co., St. Paul, MN). EASTOTAC H100R is 
available from Eastman Chemical Co., Kingsport, TN. REGALRITE 355 is 
available from Hercules Corp., Wilmington, DE. 
The data of Table 1 demonstrate the ability of a poly(hydroxyorganoate) 
such as PHN to perform as a pressure sensitive adhesive. The polymer alon 
exhibited minimal PSA properties in the peel adhesion and static shear 
tests. The polymer can be tackified to increase the peel adhesion and can 
be crosslinked to increase the time under which a load will be held in 
shear. The crosslinking experiments, which are described in this table, 
were done in static air. 
The most effective adhesives were formed when the polymer was crosslinked 
and tackified. The peel and shear values can be finetuned depending on th 
type of tackifier and degree of crosslinking that is required for a new 
PSA tape. The tackifier resins found to be the most effective were those 
of the general class of rosin esters or aromatic materials such as the 
FORAL 85, GP 2103, and PICOTEX resins. A variety of crosslinking agents 
that are able to initiate free radicals are effective at crosslinking the 
polymers of the invention. 
TABLE 2 
__________________________________________________________________________ 
Coating 
180.degree. peel 
Static 
thickness 
from (glass) 
shear 
MOF in 
Ex # 
Composition (.mu.m) 
(N/dm) (min) 
shear 
__________________________________________________________________________ 
32 PHO, 35% FORAL 85, 9% Bzophn 
23 59 s 766 CF 
33 PHO, 30% PICCOLYTE A135, 9% Bzophn 
25 13 s -- 
34 PHO, 32% PICCOLYTE A135, 5% Bzophn 
25 si 
2 [PO] -- 
35 PHO, 35% PICCOLYTE A135, 0.15% MPBT 
23 si 
18 s 1925 
CF 
36 PHO, 32% WINGTACK+, 5% Bzophn 
25 i 19 [NTR] 
-- 
37 PHO, 35% WINGTACK+, 0.15% MPBT 
28 i 14 [NTR] 
-- 
__________________________________________________________________________ 
Abbreviations: s = raspy peel, si = slightly immiscible, i = immiscible, 
PO = pop off, CF = cohesive failure, NTR = nontacky residue, Bzophn = 
benzophenone, MPBT = 
2,4bis(trichloromethyl)-6-(3methoxyphenyl)-sym-triazine (manufactured by 
Minnesota Mining and Manufacturing Co., St. Paul, MN). 
The data of Table 2 are for PHO as a pressure sensitive adhesive. This 
polymer was found to exhibit the properties of a PSA to a lesser degree 
than for PHN. 
TABLE 3 
__________________________________________________________________________ 
Coating 
180.degree. Peel 
Static 
thickness 
from (glass) 
shear 
MOF in 
Ex # 
Composition (.mu.m) 
(N/dm) (min) 
shear 
__________________________________________________________________________ 
38 PHO/N 25 1 10,000+ 
39 PHO/N, 32% GP 2103, 5% Bzophn 
25 80 s, [CF] 
6 CF 
40 PHO/N, 32% FORAL 85, 5% Bzophn 
25 112 s, [CF] 
10,000+ 
41 PHO/N, 32% PICOTEX LC, 5% Bzophn 
30 97 s, [CF] 
8595 PO 
42 PHO/N, 10% FORAL 85, 5% Bzophn 
25 32 756 CF 
43 PHO/N, 20% FORAL 85, 5% Bzophn 
25 72 [CF] 
1285 PO 
44 PHO/N, 30% FORAL 85, 5% Bwphn 
28 102 [CF] 
3319 PO 
45 PHO/N, 30% FORAL 85, 5% Bzophn 
25 73 -- 
46 PHO/N, 40% FORAL 85, 5% Bzophn 
25 99 s, [CF] 
&gt;10,000 
47 PHO/N, 40% FORAL 85, 5% Bzophn 
23 117 [CF] 
-- 
48 PHO/N, 50% FORAL 85, 5% Bzophn 
25 97 s, [CF] 
123.5 
CF 
49 PHO/N, 60% FORAL 85, 5% Bzophn 
33 8 [CF] 853 CF 
50 PHO/N, 80% FORAL 85, 5% Bzophn 
28 1 [NTR] 
1 
51 PHO/N, 55% FORAL 85, 5% Bzophn 
30 72 [CF] 
-- -- 
52 PHO/N, 20% PICOTEX LC, 5% Bzophn 
25 81 53.5 PO 
53 PHO/N, 30% PICOTEX LC, 5% Bzophn 
28 112 [CF] 
2844 PO 
54 PHO/N, 40% PICOTEX LC, 5% Bzophn 
25 147 [CF] 
10,000+ 
55 PHO/N, 60% PICOTEX LC, 5% Bzophn 
28 16 s, [CF] 
457 CF 
56 PHO/N, 80% PICOTEX LC, 5% Bzophn 
30 1 [NTR] 
1 
57 PHO/N, 50% PICOTEX LC, 5% Bzophn 
25 74 s, [CF] 
2 
58 PHO/N, 45% PICOTEX LC, 5% Bzophn 
23 72 s, [CF] 
10,000+ 
59 PHO/N, 55% PICOTEX LC, 5% Bzophn 
30 16 s, [CF] 
224 CF 
60 PHO/N, 35% FORAL 85, 9% Bzophn 
28 66 s 2075 PO/NTR 
61 PHO/N, 30% PICCOLYTE A135, 9% Bzophn 
28 11 s 10,000+ 
62 PHO/N, 32% PICCOLYTE A135, 5% Bzophn 
20 54 s, [CF] 
2620 CF 
63 PHO/N, 35% PICCOLYTE A135, 0.15% MPBT 
18 79 s 10,000+ 
64 PHO/N, 32% WINGTACK+, 5% Bzophn 
20 i 3 [PO] -- 
65 PHO/N, 32% PICOTEX LC, 5% Bzophn 
20 89 [CF] 
6060 CF 
__________________________________________________________________________ 
Abbreviations: s = raspy peel, si = slightly immiscible, i = immiscible, 
PO = pop off, CF = cohesive failure, NTR = nontacky residue, Bzophn = 
benzophenone. 
The data of Table 3 show the utility of PHO/N as a PSA. High performance 
PSAs were obtained when the tackified polymer was crosslinked, although 
PHO/N alone showed properties of a PSA. The tackifiers which provided a 
range of peels and remained compatible with the polymer were of the 
general classes of rosin acid esters and aromatic resins. A range of 
compositions using two tackifiers was developed, using PICOTEX LC and 
FORAL 85. The examples showed a change in peel values with change in 
tackifier concentration. In general, PHO/N performed extremely well as a 
PSA. The crosslinking experiments which are described in this table were 
done in static air. 
TABLE 4 
__________________________________________________________________________ 
Coating 
180.degree. peel 
Static 
thickness 
from (glass) 
shear 
MOF in 
Ex # 
Composition (.mu.m) 
(N/dm) (min) 
shear 
__________________________________________________________________________ 
66 PHO/U 13 1 10,000+ 
67 PHO/U[1], 35% FORAL 85, 9% Bzophn 
23 63 s 2184 PO/NTR 
68 PHO/U[1], 32% FORAL 85, 5% Bzophn 
18 65 s 10,000+ 
69 PHO/U[1], 35% FORAL 85, 1% Bzophn 
20 86 s 10,000+ 
70 PHO/U[1], 35% PICCOLYTE A135, 1% Bzophn 
25 26 s 10,000+ 
71 PHO/U[1], 35% PICCOLYTE A135, 0.15% MPBT 
23 si 
4 s 10,000+ 
72 PHO/U[1], 35% FORAL AX, 1% Bzophn 
23 74 [CF] 
7 CF 
73 PHO/U[1], 35% FORAL AX, 0.15% MPBT 
23 si 
62 [CF] 
16 CF 
74 PHO/U[1], 32% PICOTEX, 5% Bzophn 
23 71 273 CF/NTR 
75 PHO/U[1], 30% PICOTEX LC, 5% Bzophn 
25 89 
76 PHO/U[1], 35% PICOTEX LC, 1% Bzophn 
25 si 
82 10,000+ 
77 PHO/U[1], 35% GP 2103, 1% Bzophn 
20 99 s, [CF] 
44 CF 
78 PHO/U[1], 32% FORAL 85, 5% Bzophn 
28 52 s 10,000+ 
79 PHO/U[1], 32% FORAL 85, 1% Bzophn 
28 105 10,000+ 
80 PHO/U[2], 10% FORAL 85, 5% Bzophn 
28 4 -- 
81 PHO/U[2], 50% FORAL 85, 5% Bzophn 
30 1 s -- 
82 PHO/U[2], 20% PICOTEX LC, 5% Bzophn 
28 5 -- 
83 PHO/U[2], 30% PICOTEX LC, 5% Bzophn 
25 2 s -- 
84 PHO/U[2], 40% PICOTEX LC, 5% Bzophn 
25 1 s -- 
85 PHO/U[2], 20% FORAL 85, 5% Bzophn 
28 12 s 367 PO 
86 PHO/U[2], 30% FORAL 85, 5% Bzophn 
28 7 s 21 CF 
87 PHO/U[2], 40% FORAL 85, 5% Bzophn 
25 2 s 2290 CF 
88 PHO/U[2], 20% PICOTEX LC, 5% Bzophn 
28 23 91 PO 
89 PHO/U[2], 30% PICOTEX LC, 5% Bzophn 
23 4 s 431 PO 
90 PHO/U[2], 40% PICOTEX LC, 5% Bzophn 
23 2 s 2400+ 
__________________________________________________________________________ 
Abbreviations: s = raspy peel, si = slightly immiscible, i = immiscible, 
PO = pop off, CF = cohesive failure, NTR = nontacky residue, Bzophn = 
benzophenone, MPBT = 
2,4bis(trichloromethyl)-6-(3methoxyphenyl)-sym-triazine (manufactured by 
Minnesota Mining and Manufacturing Co., St. Paul, MN). 
The data of Table 3 show the utility of PHO/U as a PSA. High performance 
PSAs were obtained when the tackified polymer was crosslinked, although 
PHO/U alone showed properties of a PSA. The tackifiers which provided a 
range of peels and remained compatible with the polymer were of the 
general classes of rosin acid esters and aromatic resins. A range of 
compositions using two tackifiers was developed, using PICOTEX LC and 
FORAL 85. The examples showed a change in peel values with change in 
tackifier concentration. The tackified, crosslinked polymer PHO/U[1], 
containing side chains having 7-9 mole% unsaturation performed well as a 
PSA; however, PHO/U[2] which contained 12-16 mole% unsaturation in the 
side chains and provided only adhesives having lower peel adhesion. The 
crosslinking experiments which are described in this table were done in 
static air. 
TABLE 5 
______________________________________ 
Coating wt. 
thickness 
Example # 
Composition (.mu.m) % Gel 
______________________________________ 
91 PHO/U, 10% Bzophn 
24 80.88 
92 PHO/U, 5% Bzophn 
23 81.40 
93 PHO/U, 1% Bzophn 
28 41.90 
94 PHN, 10% Bzophn 26 72.11 
95 PHN, 5% Bzophn 25 73.06 
96 PHN, 1% Bzophn 26 48.71 
______________________________________ 
Abbreviations: Bzophn = benzophenone. 
A set of examples of polymer and photoinitiator was prepared to carry out 
gel content experiments. A perusal of the data in Table 5 showed that an 
increase in concentration of initiator content increased the gel content. 
TABLE 6 
______________________________________ 
Aging Time (days) 
Example # 180.degree. Peel (glass) 
25.degree. C. 
______________________________________ 
40 104 25 
41 90 25 
78 49s 25 
79 97 25 
31 102 25 
30 48 25 
74 27s 150 
62 32s [CF] 150 
10 120 [CF] 180 
14 68 [CF] 180 
19 98 [NTR] 180 
13 118 [CF] 180 
18 83 [CF] 195 
15 63 [CF] 195 
67 55 245 
32 89s, [CF] 245 
60 26s [CF] 245 
______________________________________ 
Abbreviations: CF = cohesive failure 
The peel adhesion values after aging at room temperature for a specified 
period of time of some of the Examples from Tables 1-4 are listed here. As 
can be seen in the data, the peel adhesion of the PSAs were maintained 
with time, a vital characteristic of a PSA. This data also indicates that 
the adhesives remain tacky for the aging time shown. Consequently, an open 
time greater than the aging time was maintained. 
While this invention has been described in connection with specific 
embodiments, it should be understood that it is capable of further 
modification. The claims herein are intended to cover those variations 
which one skilled in the art would recognize as the chemical equivalent of 
what has been described herein. Thus, various omissions, modifications, 
and changes to the principles described herein may be made by one skilled 
in the art without departing from the true scope and spirit of the 
invention which is indicated by the following claims.