Acrylate hot melt adhesive containing zinc carboxylate

An improved hot melt pressure sensitive adhesive composition comprises copolymerized monomeric acrylate or methacrylate ester of a non teritary alcohol, polar monomer such as acrylic acid, 2-polystyrylethyl methacrylate macromolecular monomer and sufficient zinc carboxylate to endow the composition with improved melt flow properties and cohesive strength. The invention also provides adhesive coated sheet materials comprising the adhesive composition coated onto a flexible sheet.

DESCRIPTION 
Technical Field 
This application relates to normally tacky, hot melt pressure sensitive 
adhesive compositions comprising acrylate copolymer and sheet materials 
coated therewith. 
Background Art 
Normally tacky, pressure-sensitive adhesive compositions suitable, for 
example, for use in adhesive tapes must have a requisite four-fold balance 
of adhesion, cohesion, stretchiness and elasticity. Hot melt 
pressure-sensitive adhesive compositions are thermoplastic and largely 
amorphous adhesives, softening gradually from the solid state to an easy 
flowing liquid state over a wide range of temperature. 
There are several reasons for using hot melt pressure-sensitive adhesives. 
Their use provides an energy savings because typically in use the only 
energy input that is required is that to raise the temperature of the 
composition to the liquid flowable state, thereby avoiding 
energy-intensive curing or drying steps. Furthermore, hot melt adhesives 
typically do not include solvents which often are flammable and/or toxic. 
Early hot melt adhesive compositions were 100 percent solid blends of 
thermoplastic copolymers, e.g., rubber elastomers, tackifiers, waxes, 
etc., which were required to be of a lower molecular weight to achieve the 
appropriate melt viscosity. Such low molecular weight compositions, 
however, had limited oxidative and photochemical stability and marginal 
high-temperature cohesive strength. Acrylic-based hot melt 
pressure-sensitive adhesives have been introduced to improve these 
properties while maintaining the appropriate balance of adhesive and 
cohesive strength. 
Various methods are available to improve the viscoelastic behavior of 
acrylate pressure-sensitive adhesives to make them suitable as hot melt 
pressure-sensitive adhesives. These include increasing their molecular 
weight, crosslinking, tackification, plasticization and/or chemical 
compounding. The molecular weight may be raised to improve shear strength, 
but this generally results in a composition with poor processability and a 
decrease in adhesive tack. Crosslinking, for example, by use of 
photochemical crosslinking methods requires expensive equipment and also 
results in reduced adhesive tack. The addition of tackifiers and/or 
plasticizers may improve the adhesive tack of the composition, but such 
additions typically reduce the cohesive strength and long term aging 
properties. 
Chemical compounding involves changes in chemical composition by use of 
different kinds or amounts of monomer. In general, an acrylic hot melt 
pressure-sensitive adhesive comprises a copolymer of an acrylate or 
methacrylate ester of glass transition temperature (T.sub.g) copolymerized 
with a polar monomer such as acrylic acid and a modifying monomer having a 
higher T.sub.g. Acrylic acid or acrylamide have been known to increase the 
cohesive strength of an adhesive composition because of hydrogen bonding. 
Guerin et al (U.S. Pat. No. 4,045,517) describe adhesive compositions which 
are improved by a polar interaction in the form of salt linkages between 
high T.sub.g polymer and a low T.sub.g polymer. Shah (U.S. Pat. No. 
4,337,325 and U.S. Pat. No. 4,370,380) describe reinforcing domains by 
incorporating high T.sub.g blocks with low molecular weight acrylic 
adhesive chains via hydrogen bonding. Ames (U.S. Pat. No. 4,456,741) 
describes the use of N-vinyl-2-pyrrolidone and styrene to provide hot melt 
pressure-sensitive adhesives. 
Additionally, Skoultchi (U.S. Pat. No. 4,354,008) describes hot melt 
pressure-sensitive adhesives from random acrylic copolymers containing 
chelatable comonomers and chelatable salts of transition metals. Davis et 
al (U.S. Pat. No. 3,925,282) describe thermally reversible hot melt 
adhesives comprising an acrylic copolymer containing a tertiary amine 
comonomer and an organometallic salt. Bartman (U.S. Pat. No. 4,360,638 and 
U.S. Pat. No. 4,423,182) describe a crosslinking method utilizing a 
thermally reversible ionomeric linkage between ortho-anisic acid and zinc 
ion for preparing acrylic hot melt pressure-sensitive adhesives with low 
melt viscosity. These ionomeric systems have been found by applicant, 
however, to lack the requisite four-fold balance of properties required 
for pressure-sensitive adhesive compositions. 
Recent examples of acrylic hot melt pressure-sensitive adhesive 
compositions are described in Husman et al U.S. Pat. No. 4,554,324), 
assigned to the assignee of the present application, and Schlademan (U.S. 
Pat. No. 4,551,388). Each of these references describes acrylate 
pressure-sensitive adhesives prepared by copolymerizing vinyl aromatic 
macromolecular monomer with acrylic or methacrylic acid esters and 
possibly polar monomer such as acrylic acid. This approach is recognized 
as giving acrylate-styrene graft copolymers with improved flexibility and 
general versatility by combining the attractive features of the individual 
polymer components. A review of early hot melt compositions is also 
presented by D. Bateman in Hot Melt Adhesives, (Noyes Data Corp., 3rd Ed.) 
1978. 
DISCLOSURE OF THE INVENTION 
The invention provides a normally tacky, hot melt pressure-sensitive 
adhesive composition and adhesive coated sheet materials coated therewith. 
The pressure-sensitive hot melt adhesive composition has the requisite 
four-fold balance of adhesion, cohesion, stretchiness and elasticity and 
it also has excellent processability. 
The hot melt pressure-sensitive can be coated using conventional hot melt 
coating equipment to give a stable adhesive film or coating. The adhesive 
has a suitable balance of melt flow properties and cohesive strength which 
permits such adhesive films to be longitudinally and biaxially attenuated 
to provide much thinner continuous sheets, e.g., on the order of five 
micrometers in thickness. The adhesive composition also has good creep 
resistance and, for the most part, excellent clarity, and resistance to 
oxidative and photochemical degradation. 
Specifically, the hot melt pressure-sensitive adhesive composition of the 
invention comprises copolymer consisting essentially of copolymerized 
monomers (a), (b), and (c), as follows: 
(a) about 82-92% by weight of a monomeric acrylic or methacrylic acid ester 
of a non-teritary alcohol, the alcohol having from 1 to 14 carbon atoms 
with the average number of carbon atoms being about 4-12; 
(b) about 2-5% by weight polar monomer copolymerizable with monomeric 
acrylic or methacrylic acid ester; and 
(c) about 2-15% (preferably 2-8%) by weight of 2-polystyryl-ethyl 
methacrylate macromolecular monomer; and 
sufficient zinc carboxylate to endow the composition with improved melt 
flow properties and cohesive strength. 
The preferred zinc carboxylate is selected from the group consisting of 
zinc acetate, zinc octoate, and zinc neodecanoate. The preferred amount of 
zinc carboxylate is from about 0.1 to about 5% by weight, based on the 
weight of the copolymer. 
The preferred monomeric acrylic or methacrylic acid ester is selected from 
the group consisting of butyl acrylate, isooctyl acrylate, 2-ethylhexyl 
acrylate, and isononyl acrylate. 
The preferred polar monomer is selected from the group consisting of 
acrylic acid, methacrylic acid, itaconic acid, maleic anhydride, maleic 
acid, citraconic anhydride, citraconic acid and mixtures thereof. 
The present invention also provides sheet materials coated with the hot 
melt pressure-sensitive composition described above. The sheet materials 
in accordance with the present invention comprise a backing member and a 
coating of the pressure sensitive adhesive covering at least a portion of 
one major surface of the backing member. 
DETAILED DESCRIPTION OF THE INVENTION 
In accordance with this invention, a normally tacky and pressure-sensitive 
hot melt adhesive composition comprises a polymer having in its backbone 
repeating units from acrylic or methacrylic acid ester of a non-tertiary 
alcohol, polar monomer and 2-polystyrylethyl methacrylate macromolecular 
monomer. Such monomers are disclosed in aforementioned Husman et al U.S. 
Pat. No. 4,554,324 which patent is incorporated herein by reference for 
such disclosure. 
The acrylic and methacrylic acid esters are low T.sub.g monomers of 
non-tertiary C.sub.1 to C.sub.14 alcohols, having a T.sub.g which is 
typically lower than 20.degree. C. The most preferred acrylate esters of 
this type include butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate 
or isononyl acrylate, but others are also useful. 
A useful 1-polystyrylethyl methacrylate macromolecular monomer is 
commercially available under the registered trademark "Chemlink" 4500. 
Such monomers are high T.sub.g polymeric materials, having a T.sub.g on 
the order of 90.degree. C. or higher, and a molecular weight typically on 
the order of 5,000 to 25,000. 
Preferred polar monomers include acrylic acid, methacrylic acid, itaconic 
acid, maleic acid and its anhydride, and citraconic acid and its 
anhydride. 
The zinc carboxylate is the Zn.sup.+2 salt of a difunctional organic acid 
or anhydride. Preferred zinc carboxylates include zinc acetate, zinc 
octoate, and zinc neodecanoate. The preferred amount of zinc carboxylate 
is such that the molar ratio of polar monomer to zinc carboxylate is in 
the range of about 10:1 to about 130:1. 
The preferred preparative method is to mix all components in an organic 
solvent, preferably in a mixture of ethyl acetate and methanol, in order 
to control the bulk viscosity to provide an easily mixed mixture, in the 
presence of a free radical initiator such as azo-type or peroxide 
initiator, preferably 2,2'-azobis(isobutyronitrile), and a chain transfer 
agent such as carbon tetrabromide or a mercaptan such as dodecyl mercaptan 
which are most preferably soluble in the same organic solvent. After 
suitable purging with an inert gas to expel moisture and oxygen, 
polymerization is initiated preferably at about 55.degree.-60.degree. C. 
and then the solvent removed using standard techniques. An alternative 
procedure is to prepare the terpolymer in solution and then add a solution 
of zinc carboxylate in a suitable solvent, e.g., an alcohol such as 
methanol. Still another procedure is to solvent-strip the terpolymer 
solution and then mechanically blend the zinc carboxylate into the 
solvent-free terpolymer, e.g., by extrusion, roll mixer or shear mixer. 
The resultant polymeric product produced by the afore described procedure 
is an ionomer formed of acrylic terpolymers containing ionic crosslinks as 
a result of pendant carboxylate groups associated with the zinc cation. 
Since these ionomers are not covalently crosslinked, they are 
thermoplastic and processable in conventional equipment and show a high 
degree of chain interaction. These ionomers are heat-labile acrylic 
polymers with amorphous regions of great cohesive strength by virtue of 
the ionomeric network. The character of ionomeric network is thought to be 
controlled by the relative amount of polar monomer and zinc carboxylate, 
with an increasing network or more pronounced cohesive strength being 
provided with increasing amounts of zinc carboxylate. 
By adjusting the inherent viscosity preferably to less than about 1.8 (0.15 
g/ 100 ml in solvent such as ethyl acetate) and/or by adding plasticizers 
and tackifying agents, the acrylic ionomers can be readily processed using 
standard hot melt coating equipment such as extruders. Thermal and 
photochemical stabilizers may be added during extrusion, preferably before 
solvent removal. 
The addition of zinc carboxylate to the adhesive results in improvement in 
shear-holding values and acceptable processing properties in terms of 
stable melt flow, even with severe draw-down or orientation. 
The hot melt pressure sensitive adhesive compositions of the present 
invention preferably include a tackifying resin in an amount sufficient to 
endow the composition with improved adhesive tack but not so much as to 
interfere with its adhesive properties. Preferably, the amount of 
tackifier resin is on the order of 5 to 25 parts tackifier per 100 parts 
terpolymer zinc carboxylate composition. Preferred tackifiers are referred 
to as mixed aliphatic/aromatic hydrocarbon resins. Such resins are 
typically derived from the C-5 and C-9 feedstock of petroleum hydrocarbon 
distillation processes. Commercially available examples of these 
tackifiers are Exxon's Escorez.TM. 2101, Hercules' Hercotac.TM. AD-1100, 
Goodyear's Wingtack.TM. Plus Hercules' Florel.TM. 85 is a glycerine resin 
ester tackifier which is also a good combination tackifier and plasticizer 
when higher concentrations of the metal crosslinker are used. 
Adhesive compositions are normally employed as 100 percent solids but, if 
needed, can also be applied in a suitable solvent such as ethyl acetate, 
methyl ketone, toluene, or mixtures thereof. 
Additionally, while no additives are generally needed, certain additives 
may be employed for specific purposes, including for example, fillers, 
pigments, antioxidants, ultra-violet light inhibitors, plasticizers and 
other additives typically included in conventional pressure sensitive 
adhesive compositions. 
The hot melt pressure sensitive adhesive compositions according to the 
present invention may be employed to seal boxes, adhere furniture parts, 
and for other purposes where conventional hot melt adhesives are employed. 
Such uses typically involve the application of a fillet or bead of the hot 
melt adhesive in the molten state to one or both parts to be adhered, 
joining the parts, and thereafter permitting the adhesive composition to 
cool to provide a firm adhesive bond. More often, the adhesive composition 
of the present invention is applied to a backing, such as a flexible 
backing formed of any of a variety of conventional backing materials such 
as paper, e.g., Kraft paper or crepe paper, plastic film, which may be 
primed to provide a more aggressive adhesive bond thereto, e.g., polyester 
films such as polyethylene terephthalate, polypropylene, polyethylene, 
etc., woven or nonwoven backing materials such as that used in packaging 
and fastening tapes. 
The adhesive composition may be applied with conventional hot melt adhesive 
application equipment such as by use of extruders which extrude a sheet or 
fillet of molten adhesive or by merely heating a container of adhesive 
composition and removing a portion of the molten adhesive with a suitable 
device for application where needed. Such processing equipment is 
conventional and well known in the adhesive art. 
Further modifications may be made in the adhesive composition described 
without departing from the scope of the claims.

EXAMPLES 
The following examples are provided to further illustrate the claimed 
invention. All parts described in the examples are by weight, unless 
otherwise specified. 
Examples 1-10 and Controls A-C 
The preferred adhesive composition according to the invention, having the 
requisite four-fold balance of adhesion, cohesion, stretchiness, and 
elasticity is a terpolymer of isooctylacrylate (IOA), 2-polystyrylethyl 
methacrylate macro-molecular monomer (PSMA), and acrylic acid (AA) with 
the acrylic acid partially neutralized with zinc cation most preferably 
with a ratio of IOA:PSMA:AA of about 92-93:3-4:4. The adhesive properties 
of various adhesive compositions identified as Examples 1-10 are 
summarized in Table 1. Examples 1-10 had acceptable processing ability, (a 
broad melt viscosity profile) and a good elastic modulus. A description of 
the preparation of Examples 1-10 and Control A-C is given below. 
Control A 
General Procedure for IOA/PSMA/AA (93/3/4) 
A three-liter reaction flask, equipped with condenser, nitrogen inlet, 
temperature control, heating means and stirrer was charged with 200 g. of 
methanol, 930 g. of isooctyl acrylate monomer (IOA), 40 g. of acrylic acid 
monomer (AA), 800 g. of ethyl acetate, 30 g. of 2-polystyylethyl 
methacrylate macromolecular monomer (PSMA) (available as CHEMLINK.TM. 4500 
from Sartomer Chemical Co.), 0.60 g. of carbon tetrabromide and 2.12 g. of 
2,2'-azobis(2-methyl-propionitrile). The reaction mixture was stirred to 
dissolve the PSMA and then deaerated by repeated applications of vacuum 
and nitrogen (three times) while being heated to 55.degree. C. Tendency to 
exotherm was held below 64.degree. C. by intermittent cooling in an 
ice-water bath. The reaction was continued for 24 hours at 55.degree. C. 
with constant stirring. The reaction product was transferred to a aluminum 
tray which was placed in an oven to remove the solvent. Analysis revealed 
a number average (MN) molecular weight of 1.48.times.10.sup.5, a 
polydispersity of 2.96, and an inherent viscosity run in ethyl acetate at 
a concentration of 0.15 g. per 100 ml. of 0.60. 
Control B 
Preparation of Acrylic Hot Melt PSA of Composition IOA/PSMA/AA (92/4/4) 
The identical procedure of Control A was followed except for the charging 
of the two monomers (IOA and AA) and the macromolecular monomer (PSMA). 
These charges were 920 g. isooctyl acrylate (IOA), 40 g. acrylic acid (AA) 
and 40 g. of polystyrylethyl methacrylate (PSMA). The analytical results 
of this reaction product revealed a number average (MN) molecular weight 
of 1.53.times.10.sup.5, a polydispersity of 2.85 and an inherent viscosity 
of 0.63. 
Control C 
Preparation of Acrylic Hot Melt PSA of Composition IOA/AA (96/4) with 1.00% 
Zinc Octoate 
A two-liter reaction flask equipped with condenser, nitrogen inlet, 
temperature control, heating means, and stirrer was charged with 100 g. of 
methanol, 384 g. of iso-octyl acrylate monomer (IOA), 16 g. of acrylic 
acid monomer (AA), 390 g. of ethyl acetate, 4 g. of zinc octoate, 0.24 g. 
of carbon tetrabromide and 0.84 g. of 2,2'azobis (2-methyl-propionitrile). 
The mixture was deaerated by repeated applications of vacuum and nitrogen 
(three times) then heated to 5.degree. C. with stirring (250 RPM) and 
nitrogen purge. The exotherm was held below 64.degree. C. by intermittent 
cooling in an ice-water bath. The reaction was continued for 24 hours at 
55.degree. C. with constant stirring. The resulting solution was 
transferred to a TEFLONTM.TM.-lined aluminum tray which was placed on an 
oven to remove the solvent. Analysis revealed a number average (M.sub.N) 
molecular weight of 1.70.times.10.sup.5, a polydispersity of 3.45, and an 
inherent viscosity run in ethyl acetate at a concentration of 0.15 g. per 
100 ml. of 0.96. 
EXAMPLES 1-10 
Preparation of Ionomeric, Acrylic Hot Melt PSAs From IOA/PSMA/AA (93/3/4 
and 92/4/4) 
With Varied Amounts of Zinc Carboxylates 
The general procedure described in Procedure A (Control A) was followed in 
the preparation of Examples 1 through 10 except for the addition of zinc 
carboxylate. The actual charge of zinc carboxylate is based upon a total 
weight of 1000 grams of monomers and the weight percentage of zinc 
carboxylate (e.g., acetate, octoate or decanoate) is reported in Table I. 
TABLE I 
__________________________________________________________________________ 
180.degree. 
Monomer Zn Carboxylate 
C.T..sup.2 
Peel Shear 
Ex. No. 
& Ratio (Anion) 
(wt. %) 
I.V..sup.1 
(.mu.m) 
(N/100 mm) 
(Min.) 
__________________________________________________________________________ 
1. IOA/PSMA/AA 
Acetate 
1.22 0.94 
23 57 282.sup.3 
93/3/4 
2. " Acetate 
1.00 0.85 
25 59 320s 
3. " Octoate 
1.33 0.71 
23 64 380 
4. " Octoate 
1.00 0.70 
23 75 133 
5. IOA/PSMA/AA 
Acetate 
1.22 0.77 
23 51 402s 
92/4/4 
6. " Acetate 
0.49 0.71 
23 62 128s 
7. " Octoate 
1.33 0.70 
23 62 484 
8. " Octoate 
1.00 0.76 
23 62 233 
9. " Octoate 
0.67 0.74 
25 70 138 
10. " Decanoate 
2.84 0.53 
23 57 372 
Control A 
IOA/PSMA/AA 
None None 0.60 
23 79 10s 
93/3/4 
Control B 
IOA/PSMA/AA 
None None 0.63 
23 79 29s 
92/4/4 
Control C 
IOA/AA Octoate 
1.00 0.96 
23 70 5s 
96/4 
__________________________________________________________________________ 
.sup.1 "I.V." means inherent viscosity run at 30.degree. C. in ethyl 
acetate at 0.15 g/100 ml. 
.sup.2 "C.T." means coating thickness in micrometers (.mu.m) 
.sup.3 "s" means the adhesive split or it suffered cohesive failure. 
As shown in Table I, increased shear-holding values were obtained when 
macromolecular monomer (PSMA) and zinc carboxylate were used together. 
Table I shows a similar increase in shear-holding value was observed in 
macromolecular monomer-containing adhesive formulations with low 
macro-molecular monomer content, e.g., IOA/PSMA/AA (93/3/4). 
Examples 11-16 verify that the preferred addition of zinc carboxylate is by 
in situ, (batch) addition. Examples 11-16 consisted of IOA/PSMA/AA 
(92/4/4) with the amount and type of zinc carboxylate shown in Table II 
below. 
EXAMPLES 11-16 
TABLE II 
______________________________________ 
Effect of Mode of Adding Zinc Carboxylates 
Type 
Ex. Zn Carboxylate of Ad- CT 180.degree. Peel 
Shear 
No. (anion) (wt. %) dition 
(.mu.m) 
(N/100 mm) 
(min.) 
______________________________________ 
11 Octoate 1.00 in situ 
24 62 233 
12 Octoate 1.00 post- 24 77 82s 
polymn 
13 Acetate 1.22 in situ 
24 51 402 
14 Acetate 1.22 post- 23 75 57s 
polymn 
15 Decanoate 1.41 in situ 
23 84 25s 
16 Decanoate 1.41 post- 23 81 26s 
polymn 
______________________________________ 
EXAMPLE 17 
IOA/PSMA/AA/Zn Octoate (91/4/4/1) 
A mixture of isooctyl acrylate (100 kg), acrylic acid (4.35 kg), 
macromolecular monomer having a molecular weight of 13,000 and being 
commercially available under the trademark "CHEMLINK" 4500, zinc octoate 
(1.1 kg), ethyl acetate (87 kg), methanol (22 kg), carbon tetrabromide 
(65.4 g.), and 2,2'-azobis(isobutyronitrile) free radical initiator 
available under the trade designation "VAZO" 64 from the E.I. DuPont 
Company (229 g.) was charged into a 285-liter reactor, purged by vacuum 
and nitrogen gas and then heated to 55.degree. C. and kept at this 
temperature for 24 hours. Vacuum reflux and jacket cooling were used to 
control the exotherm. The solution polymer was then solvent-stripped and 
the hot melt collected in 20-liter pails. Gel permeation chromatography 
(GPC) analysis showed a number average molecular weight (Mn) of 
2.77.times.10.sup.5 and polydispersity of 2.59. Inherent viscosity at 
30.degree. C. (0.15 g/100 ml tetrahydrofuran [THF]) was 1.22. Adhesiveness 
testing of 20 micrometer extruded adhesive coating revealed a 180.degree. 
peel strength of 48 N/100 mm and a shear strength of 1364 minutes. 
EXAMPLE 18 
IOA/PSMA/AA/Zn Acetate (92/3/4/1) 
This was prepared as in Example 1 from isooctyl acrylate (100 kg), acrylic 
acid (4.8 kg), macromolecular monomer ("CHEMLINK" 4500) (324 kg), zinc 
acetate (1.1 kg), ethyl acetate (87 kg), methanol (21.7 kg), carbon 
tetrabromide (65.3 g.), and free radical initiator ("VAZO" 64) (228 g.). 
GPC analysis showed Mn of 2.58.times.105 and a polydispersity of 2.82. 
Inherent viscosity at 30.degree. C. (0.15 g/100 ml THF) was 1.14. Adhesive 
testing revealed a 180.degree. peel strength of 46 N/100 mm and a shear 
time of 379 minutes. 
Test Methods 
Gel Permeation Chromatography 
The molecular weight distribution of the adhesive compositions was 
characterized by conventional gel permeation chromatography (GPC) using a 
Hewlett-Packard Model 1084B, high performance liquid chromatograph 
equipped with ultra STYRAGEL.RTM. columns and differential refractometer 
and UV detectors. All GPC calculations were performed on a Hewlett-Packard 
Model 3388 integrator and all molecular weight averages are polystyrene 
equivalent molecular weights. The molecular weight averages and 
polydispersities were calculated according to accepted practices. Percent 
incorporated molecular monomer was calculated using a UV detector. 
Percent Incorporated Carboxylic Acid 
The percent incorporated carboxylic acid was determined using conventional 
titration of the adhesive dissolved in tetrahydrofuran against a sodium 
hydroxide standard solution to the phenolphthalein end point. 
Inherent Viscosity Measurements 
The inherent viscosity (I.V.) was measured by conventional means using a 
Cannon-Fenske #50 viscometer in a water bath controlled at 30.degree. C. 
to measure the flow time of 10 ml of a polymer solution (0.15 g of polymer 
in 100 ml of ethyl acetate or tetrahydrofuran). Both polymer solutions and 
controls were run under identical conditions. 
PSA Test Methods 
Tape samples were prepared by extrusion-coating onto primed, 35 micrometer 
polyester film using a 19 mm Haake.RTM. extruder equipped with a draw die 
(101 mm.times.50 micrometers) and a Rheocord.RTM. rheometer. 
The standard tests are described in detail in various publications of the 
American Society for Testing and Materials (ASTM), Philadelphia, Pa. and 
the Pressure Sensitive Tape Council (PSTC), Glenview, Ill. The standard 
test methods are described in detail below. The reference source of each 
of the standard test methods is also given. 
SHEAR STRENGTH 
Reference ASTM: D3654-78; PSTC-7) 
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 terms of time (in minutes) required to pull a standard area of 
adhesive 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 12.5 mm by 12.5 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 
panel forms an angle of 178.degree. with the extended tape free end which 
is 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. less 
than 180.degree. is used to negate any peel forces thus insuring that only 
the shear forces are measured in an attempt to more accurately determine 
the holding power of the tape being tested. The time elapsed for each tape 
example to separate from the test panel is recorded as the shear strength. 
PEEL ADHESION 
(Reference: ASTM D3330-78 PSTC-1 (11/75) 
Peel adhesion is the force required to remove a coated flexible sheet 
material from a test panel measured at a specific angle and rate of 
removal. In the examples, this force is expressed in Newtons per 100 mm 
(N/100 mm) width of coated sheet. The procedure followed is: 
1. A 12.5 mm width of the coated sheet is applied to the horizontal surface 
of a clean glass test plate with at least 12.7 lineal cm in firm contact. 
A hard rubber roller is used to apply the strip. 
2. The free end of the coated strip is doubled back nearly 
touching itself so the angle of removal will be 180.degree.. The free end 
is attached to the adhesion tester scale. 
3. The glass test plate is clamped in the jaws of a tensile testing machine 
which is 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 is recorded as the tape is peeled from the 
glass surface. The data is reported as the range of numbers observed 
during the test. 
While this invention has been described in connection with specific 
embodiments, it should be understood that it is capable of further 
modification. For example the disclosed solution polymerization method of 
making the polymeric materials comprising the hot melt pressure sensitive 
adhesive compositions of the present invention may be substituted by other 
conventional polymeric processes such as suspension, emulsion or bulk 
polymerization techniques. It should be understood that certain 
modifications may be required in such techniques to facilitate or optimize 
their use to produce the claimed hot melt pressure sensitive adhesive 
compositions. 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 here.