Note: Descriptions are shown in the official language in which they were submitted.
2 ~
LATEX BASED ADHESIVE PREPARED
BY EMULSION POLYMERIZATION
The present invention relates to an adhesive.
More particularly, the present invention relates to such
an adhesive having one polymeric component adapted to
provide adhesive properties and another polymeric
component adapted to provide tackifying properties.
More particularly still, the present invention relates
to such an adhesive wherein both the adhesive and
tackifier components are separately prepared by emulsion
polymerization.
Aqueous collodial dispersions of polymers,
which are referred to in the art as latexes, are
generally known to be useful as adhesives. A wide
variety of adhesive formulations have been prepared that
are specially adapted for particular uses. While
latexes generally provide good adhesion to various
substrates, it is often desirable to include a secondary
component, generally a low molecular weight emulsified
resin which is employed in order to provide initial
stickiness or tack to the adhesive formulation. Such a
component is referred to as a tackifier.
35,635-F -1
~` 2~'2~2
Certain prior art adhesive formulations have included a
latex based adhesive component such as a latex of a
styrene/butadiene copolymer, and conventional tackifiers
such as rosin esters, or other suitable tackifier, see
e.~. U.S. Patent 4,189,419. The properties of the
adhesive composition may be adjusted by appropriate
selection of both the type and amounts of tackifier or
adhesive component employed in order to provide a
resulting composition having the desired properties.
However, such adhesive formulations have
certain undesirable properties. For example, the
process for dispersing the tackifying resin adds
unnecessary complexity and additional cost to the
5 formulation. In addition, such formulations often -~
demonstrate insufficient coalescence between resin
particles and latex particles, thereby necessitating
using excessive amounts of tackifier resin. This
problem has been previously disclosed in U.S. Patent
4,445,959, Column 12. Also, because relatively high
levels of surfactant are required to disperse the
tackifying resin adhesive properties are often
detrimentally affected. Finally, under some conditions
of high shear such as may be encountered during
application of adhesives, these previously known
adhesive formulations may lack sufficient stability.
Techniques are already known for the
preparation of low molecular weight polymers via free-
radical, emulsion polymerization processes. Typically,
~uch techniques include initiation by organic peroxides
or inorganic persulfate compounds, and the use of large
quantities of a suitable chain transfer agent such as a
halogen compound, or a mercaptan compound.
35,635-F -2-
. , , :
2~2~
Latex based adhesive components, especially
copolymers of styrene and butadiene are similarly known.
Suitable examples of such adhesive components are
disclosed in U.S. Patent 4,419,481.
In GB Yatent 2,137,212, there is disclosed a
tackified styrene/butadiene polymer adhesive made by
preparing an emulsion polymerized adhesive component in
the presence of an emulsion of a synthetic tackifier
resin or rosin derivative.
In U.S. Patent 4,438,232, a latex adhesive
resin is disclosed. In l.S. Patents 4,013,824,
4,064,377 and 4,145,494, emulsion processes for
15 preparing polymers with a mercaptan as a chain transfer
agent are disclosed.
It would be desirable to prepare by emulsion
polymerization a latex of an ultra low molecular weight
20 polymer suitable for use as a tackifying resin which
does not require dispersing a solid polymer in water by
use of surfactant.
In addition, it would be desirable to provide a
25 latex based adhesive formulation which does not require
the presence of a conventional, emulsified tackifier
resin.
Finally, it would be desirable to provide an
30 adhesive formulation wherein both the adhesive component
and the tackifier component are prepared entirely by
emulsion polymerization.
According to the present invention, there is
35 now provided a latex based adhesive, the adhesive
characterized by having at least two polymeric
35,635-F -3-
2~2~
components, the first polymeric component (adhesive
component) comprising a random interpolymer of at least
one hard monomer and at least one soft monomer and
optionally a copolymerizable carboxylic acid and having
a glass transition temperature, Tg, of from -70C to
-5C, and the second polymeric component (tackifier
component) that is compatible with the adhesive
component, and having a number average molecular weight
less than 5,000 and a Tg from -10C to 50C, provided
further that both the adhesive component and tackifier
component have been separately prepared by emulsion
polymerization techniques.
The latex based adhesive of the invention is
particularly useful as a pressure sensitive adhesive for
coating conventional substrates to form adhesive tapes
in the preparation of carpet backings. It may also be
employed as a laminating adhesive, such as in film to
film laminations or film to paper laminations and in
other adhesive applications.
Desirably, the adhesive component comprises
from 95 to 20 percent and the tackifier component
comprises from 5 to 80 percent of the invented
composition, measured on a dry weight basis.
As used herein, "glass transition temperature"
(Tg) is determined by Dynamic Mechanical Spectroscopy
(DMS) or by Differential Scanning Calorimetry (DSC) at a
rate of 10C/min. utilizing a duPont 1090 model or
equivalent calorimeter. Moreover, as used herein
"compatibility" may be said to exist if respective
polymers, upon mixing, demonstrate a single Tg or a
35,635-F -4_
353
--5--
narrowing of the difference in separately determined
Tg's.
Molecular weights of polymers are measured by
size exclusion chromatography (SEC) using a 2-4000 HXL
and 1-2500 HXL column calibrated for low molecular
weight polymers. Samples are prepared utilizing
approximately 0.1 gram of polymer dissolved in 20
milliliters of tetrahydrofuran.
By the term "soft monomer" is meant addition
polymerizable monomers which, if homopolymerized, would
yield a homopolymer having a glass transition
temperature (Tg) less than 25C. Suitable examples of
15 soft monomers include esters of unsaturated acids and
saturated alcohols having from 3 to 15 carbons, such as
n-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl
acrylate, and butyl methacrylate; and conjugated
aliphatic dienes having from 4 to 12 carbons such as
20 1,3-butadiene, 2-methyl-1,3-butadiene, pentadiene, and
2-chloro-1,3-butadiene. Preferred soft monomers are n-
butyl acrylate and 1,3~butadiene. A most preferred soft
monomer is 1,3-butadiene.
By the term "hard monomers" is meant addition
polymerization monomers other than carboxylic acids,
which if homopolymerized, would yield a homopolymer
having a Tg greater than 25C. Suitable examples of
30 hard monomers include esters of unsaturated acids having
from 3 to 10 carbons such as tert-butyl acrylate, methyl
methacrylate, and tert-butyl methacrylate; and C8_16
monovinylidene aromatic monomers such as styrene,
a-methylstyrene, vinyl toluenes, bromostyrene, etc. A
35 preferred hard monomer is styrene.
35,635-F -5-
2~2&~
Suitable copolymerizable carboxylic acids are
C2_l0 ethylenically unsaturated carboxylic acids such as
itaconic acid, acrylic acid, and maleic acid. A
preferred copolymerizable carboxylic acid is itaconic
acid.
Preferably, the tackifier component comprises
an interpolymer of at least one hard monomer and
optionally one or more soft monomers as well as a
copolymerizable ethylenically unsaturated carboxylic
acid. In a highly preferred embodiment, the tackifier
component is prepared by emulsion polymerization of the
soft and hard monomers, and optionally a carboxylic acid
containing monomer in the presence of a large quantity
of chain transfer agent. By the term "large quantity"
is meant a sufficient quantity of chain transfer agent
to provide a latex of a interpolymer having a molecular
weight of less than 5,000. As used herein, molecular
weights are determined by the techniques of hydrodynamic
chromatography. Suitable chain transfer agents include
carbon tetrachloride, bromoform, and alkyl or aralkyl
mercaptans having 2 to 20 carbons. Preferred chain -
transfer agents are aliphatic mercaptans containing from
8 to 20 carbon atoms. A highly preferred aliphatic
mercaptan is tertiary dodecyl mercaptan. Desirably, the
chain transfer agent is employed in an amount from 1
percent to 20 percent by weight, preferably from 5 to 15
percent by weight based on reacted monomer weight.
3o
Respective amounts of monomers are employed in
the polymerization to prepare a tackifier component
comprising from 30 percent to 100 percent by weight hard
monomer, from 70 percent to 0 percent soft monomer and
up to 10 percent of a copolymerizable carboxylic acid.
A preferred composition comprises from 60 to 90 percent
35,635-F -6-
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2 ~ 2 ~ 2
hard monomer, 40 to 10 percent soft monomer, and l to 5
percent carboxylic acid. As used throughout the
specification and claims, such values are based on total
ethylenically unsaturated monomer content of the polymer
latex and exclude polymerized mercaptan content. A most
preferred tackifier component comprises an interpolymer
of styrene, butadiene and an unsaturated carboxylic
acid. The number average molecular weight of the
tackifier component is preferably from 1,000 to 4,000.
Suitable adhesive component interpolymers
comprise from 30 to 90 percent soft monomer, from 70 to
10 percent hard monomer, and optionally up to 10 percent
of a copolymerizable carboxylic acid comonomer. A
preferred composition comprises from 50 to 80 percent
soft monomer, from 50 to 20 percent hard monomer, and 1
to 5 percent unsaturated carboxylic acid. The foregoing
percentages are based on total ethylenically unsaturated
monomer weight. The adhesive component is most
preferably an interpolymer of styrene, butadiene and a
copolymerizable carboxylic acid. A mercaptan, if
present, is employed in an amount from 0.01 to 5.0
percent of the adhesive component.
The adhesive component may additionally
comprise a crosslinking monomer such as divinyl benzene,
trimethylol propane triacrylate, etc.
The adhesive and tackifier components of this
invention may be prepared using conventional emulsion
polymerization techniques. Thus, for example, the
monomers and chain transfer agent employed are typically
dispersed with agitation sufficient to emulsify the
mixtures in an aqueous medium containing known
emulsifying agents (i.e, surfactants) as well as other
35,635-F -7-
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.
ingredients conventionally employed in the art as
polymerization aids (e.g., chelating agents, seed latex,
bactericides, antifoamants). Such monomers are then
subjected to polymerization with the aid of a
conventional source for generating free radicals, such
as free radical initiators or activating radiation. The
polymerization may be conducted in continuous or batch
mode.
The final product is prepared by combining the
respective components utilizing conventional compounding
or blending equipment. Additional conventional
additives such as plasticizers, surfactants, fillers,
antioxidants, pigments, thixatropic aids, and flow aids,
may also be incorporated into the finished formulation.
Having described the invention, the following
examples are provided as further illustrative of the
invention and are not to be construed as limiting.
Unless otherwise indicated, all parts, percentages, and
ratios herein are based on dry solids weight.
Manufacture of the Tackifier Component
Sample 1
(a) A monomer feed charge was prepared
comprising 98 parts of styrene, 10 parts t-dodecyl
mercaptan and 5 parts of carbon tetrachloride.
3o
(b) A second monomer feed charge was prepared
comprising 18.7 parts of water, 2 parts of itaconic acid
and 0.14 part of sodium hydroxide.
(c) An aqueous feed charge was prepared
comprising 22.0 parts of water, 0.5 parts sodium dodecyl
35,635-F -8-
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benzene sulfonate surfactant, and 0.7 parts sodium
persulfate.
To a one gallon (3.8 liter) stainless steel
reactor having an agitator and several inlets for the
addition of the aforementioned charges was added 61.0
parts of deionized water, 0.01 part of a 1 percent
solution of the trisodium salt of N-(hydroxyethyl)
ethylene diamine triacetic acid (chelant), 3.5 part of a
305 Angstrom number average diameter, 96:4 weight ratio
styrene/acrylic acid copolymer latex. The reactor was
purged with nitrogen, agitated at 350 rpm and heated to
90C. Monomer feed charge (a) was added to the reactor,
beginning at time-0 minutes over a total period of 390
minutes. After 15 minutes, monomer charge (b) was added
over a total period of 330 minutes. Charge (c) was
added to the reactor beginning at time t=0 for a total
of 330 minutes. After complete addition of all charges
reaction was continued at 90C under nitrogen atmosphere
for one hour.
The resulting latex (styrene/itaconic acid =
98/2) contained 10 percent t-dodecyl mercaptan and 5
25 percent carbon tetrachloride remnants and had apparent -
number average molecular weight 1,600.
Sample 2
In a manner similar to Sample 1, ultra low
3 molecular weight latex particles were prepared with a
monomer composition of 78 parts styrene, 20 parts
butadiene and 2 parts itaconic acid. The content of
t-dodecyl mercaptan was 10 percent. Carbon
tetrachloride remnant content was 5 percent.
35,635-F -9_
2 ~
--1 o--
Samples 3-7
Additional tackifier components were prepared
by a continuous addition emulsion process similar to
that disclosed in Sample 1 excepting that a mixture of
styrene and butadiene monomers was charged as monomer
charge (a). The amounts of monomers were varied to
provide the polymer compositions indicated in Table I. -
Monomer charge (a) containing styrene and butadiene in
total equivalent amounts equal to the equivalent of
styrene used in Sample 1, along with carbon
tetrachloride and t-dodecyl mercaptan, was added to the
reactor, beginning at time t=0 minutes for a total of
270 minutes. Remaining charges (b) and (c) are as
previously described. Charge (b) was added to the
reactor beginning at time t=15 minutes for a total of
210 minutes. Charge (c) was added to the reactor
beginning at time t=0 for a total of 300 minutes.
Following addition of all feed streams, the reactor
contents were agitated for an additional 60 minutes at
90C under nitrogen atmosphere. The reactor was cooled
and the resulting latex recovered.
Results of the polymerization are contained in
Table I.
3o
35,635-F -10-
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Table I
Feed Chain Transfer
Monomer Agent Content Apparent
Ratio (%) Number
Sample Styrene/- Average
Butadiene~- .Molecular
Itaconic t-dodecyl CCl~ Weight
. Acld mercaptan _ .
3 78/20/2.0 10 5 2,200
4 68/30/2.0 10 5 2,400
58/40/2.0 10 5 2,600
6 88/10/2.0 15 5 1,330
7 88/10/2.0 _ 20 5 1,100
Sample 8
Monomer charge (a) was prepared comprising 68
parts of styrene, 30 parts of butyl acrylate and 2 parts
of t-dodecyl mercaptan.
Monomer charge (b) was prepared comprising 18.0
parts of deionized water, 2.0 parts of itaconic acid and
0.22 parts of sodium hydroxide.
Monomer charge (c) was prepared comprising 16.0
parts of deionized water, 0.18 parts of sodium
hydroxide, 1.0 parts of sodium dodecyl benzene sulfonate
surfactant, and 1.5 parts of sodium persulfate.
To a one gallon stainless steel reactor having
an agitator and several inlets for addition of the
aforementioned charges were added 77.0 parts of
deionized water, 0.01 parts chelant, 10.0 parts of
carbon tetrachloride and 3.5 parts of a 305 Angstrom
number average diameter, 96:4 weight ratio
.
35,635-F -11-
~2~
styrene/acrylic acid copolymer seed latex. The reactor
was purged with nitrogen, agitated at 350 rpm and heated
to 90C. Monomer charge (a) was added to the reactor at
time t-0 for a total of 270 minutes, monomer charge (b)
was added to the reactor beginning at t=0 for total of 6
minutes. Monomer charge (c) was added to the reactor
beginning at time t=0 for a total of 270 minutes.
Reaction was continued for one hour at 90C following
complete addition of all the charges.
Sample 9
The procedure of Sample 8 was repeated
excepting that a mixture of styrene, butadiene and butyl
acrylate monomers is employed as monomer charge (a).
Results are contained in Table II.
Table II
Monomer Ratio in Feed Chain
Trans- Apparent
~fer Number
Sample Agent Average
Buta- Butyl Ita- Con- Molecular
Styrene diene ACartYel~ cAocniidc tent Weight
_ .
8 68 0 3 2 2 3,800
9 68 2010 2 2 3,300
3o
35,635-F -12-
2Q25~62
,
-13-
Manufacture of Adhesive ComPOnent
Sample A
A carboxylated styrene/butadiene latex was
prepared by the continuous feed polymerization of ~0
parts butadiene, 28 parts styrene, 2 parts itaconic
acid, 2.25 parts t-dodecyl mercaptan, and 3.0 parts
carbon tetrachloride. The resulting latex had a
particle size of about 1050 Angstroms.
Sample B
A carboxylated styrene/butadiene latex was
prepared essentially according to the method of Sample
10, excepting that the amount of t-dodecyl mercaptan was
measured to 2.75 parts. The resulting latex had a
particle size of about 1050 Angstroms.
Sample C
A carboxylated styrene/butadiene latex was
prepared substantially according to the technique of
Sample A, excepting that 65 parts of butadiene, 33 parts
styrene, 2 parts itaconic acid, 2 parts t-dodecyl
mercaptan and 3 parts of carbon tetrachloride were
employed. The resulting latex had a particle size of
1050 Angstroms.
Preparation and Testin~ of Two ComPonent Adhesive
3o
Examples 1-9
Several tests were used to evaluate the
adhesion of various formulations to specific substrates
as well as for specific end-use applications.
35,635-F -13-
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-14-
(a) Adhesion to Specific Substrates: In this
method, a substrate to which adhesion was to be
determined was secured to a glass plate using double-
sided adhesive tape. Two parallel strips of double-
sided adhesive tape were then attached to the substrateapproximately 6 inches (15.24 cm) apart. The adhesive
was applied in an even film to the exposed surface of
the substrate between the strips of tape. A reinforcing
material (i.e., cheese cloth) was laid evenly over the
adhesive and the strips of double-sided adhesive tape.
The composite was allowed to dry for 24 hours and then
conditioned overnight at a constant temperature of
70 to 72F (21 to 22C) and 50 percent relative humidity.
One inch (2.54 cm) wide strips were cut between the
strips of adhesive tape. The cheese cloth and the given
substrate were separated at the double-sided tape and
inserted in opposite jaws of an Instron~ adhesion
tester. Peel adhesion (180) was then measured at peel
rates of 2 inch/min. (5.08 cm/min.) and 20 inch/min.
(50.8 cm/min.).
Several adhesive systems were formulated and
evaluated by test method (a) to determine adhesion to
untreated polypropylene film (Mobil Bicor~ 278T).
Results are contained in Table III.
35,635-F -14-
2~?J~2
-15-
Table III
Peel
Latex Adhesion,
(kg/cm)
Sample B 1 9 (0.34)
Example 1 4.5 (0.81)
(Sample B/
Sample 2/* )
* blended in a 60/40 ratio
The results indicate that improved peel
adhesion was obtained by a blend of an adhesive
component and a tackifier component according to the
15 inventiOn.
Adhesion Test for Film To Paper Laminates:
This test was used to determine the performance of a
given adhesive system for film to paper or paperboard
laminated structures. Adhesive was applied to a 7x14
inch ( 17.8 cm x 35.6 cm) unbleached Alabama Kraft~
paperstock ( 20 point). The adhesive was drawn down in
the cross machine direction using a No. 31 mayer rod.
After the adhesive was drawn down, the untreated side of
25 a polypropylene film (Mobil Bicor~ 278T) was placed on
the wet adhesive without applying pressure. The
laminate was allowed to air dry for 24 hours at room
temperature. Then several 1 /2 inch (1.27 cm) cuts were
30 made on the laminates in the machine direction. The
laminate was attached in a horizontal position and the
film edge was held between the thumb and index finger
and pulled by hand in a direction about 135 to the
horizontal plane. Two rates of pull, a slow rate
35 (approximately 180 inches/minutes (457.2 cm/minutes))
and a fast rate (approximately 720 inches/minutes
35,635-F -15-
.
2~2~ 2
-16-
(1828.8 cm/minutes)) at two temperatures 40F and 72F
(4C and 22C~ were employed.
The method of bond failure was then evaluated.
Fiber tear (FT) was determined by the presence of fiber
particles on the separate film surface. Adhesive
failure (AF) indicates clean separation of either the
paperboard or the film from the adhesive layer while
cohesive failure (CF) indicates separation of the
adhesive layer into two or more portions.
The same adhesive systems which were evaluated
for basic adhesion to untreated polypropylene film were
evaluated by test method (b) to determine the adhesive
ability to bond untreated polypropylene film to
; paperboard. Results are contained in Table IV.
Table IV
..
72F (22C) 40F (4C)
Adhesive System _
Slow Fast Slow Fast
Pull Pull Pull Pul
Sample A AF AF AF AF
Example 2 FT FT FT FT/AF
(Sample B/
Sample 2*)
* blended in a 60/40 ratio
Inspection of the data in the above table shows
that the adhesive component by itself does not give
suitable fiber tear properties. However, when such
components were formulated with a tackifier component
according to the invention, the resulting adhesive
35,635-F -16-
, .
2 ~ g ~ 2
demonstrated that a system can effectively bond
untreated polypropylene film to other substrates such as
paper stock or paperboard.
(c) 180 Peel Adhesion Test for Film-Paper
_minates: Laminates were prepared as described in the
above section (b). One inch (2.54 cm) wide cuts are
made through the film and the paperboard. The films
were pulled on an Instron~ adhesion tester at 180 with
10 a rate of pull of 12 inch/min. (30.48/min.) at room
temperature. The force required to effect destruction
of the bond was recorded along with the mode of failure.
Film/Paper Adhesion
Several adhesive systems were evaluated by test
method (c) to determine adhesion between corona treated
film (Oppalyte~ TW-3 available from Mobil Chemicals,
Inc.) and paperboard substrates. Sample portions of
film were coated with various adhesive formulations.
Results are contained in Table V.
3o
35,635-F -17-
2~2~
-18-
Table V
__ 180 Peel
Adhesive lbs/in
(k~/cm)
. . , .
Sample C 480 (86.4)
Example 3 600 (108)
(Sample C/Sample 3; 50/50)
Example 4 9O (162)
(Sample C/Sample 4; 50/50)
Example 5 640 (115)
(Sample C/Sample 5; 50/50)
Example 6 780 (140)
15(Sampl~ C/Sample 6; 50/50)
Example 7 850 (153)
(Sample C/Sample 7; 50/50)
Comparative Example 1 570 (103)
(Sample C/PS*; 50/50)
*Comparative, PS is a low molecular weight polystyrene
dispersion tackifier, Piccolastic A-75~, available from
Hercules, Inc.
The results of the above testing indicate that
adhesion equally, or even exceeding that obtainable
utilizing conventional adhesive formulation technology
utilizing conventional tackifiers, can be obtained
according to the present invention.
(d) Adhesive Test for Film to Film Laminates:
This method consists of applying the adhesive to primary
film substrate and drawing it down the web using a No. 3 `
mayer rod, which is equivalent to applying approximately
0.5 to 0.7 lbs per/1000 ft2 (0.22 to 0.32 kg/92.9 sq.
35,635-F -18-
:
:
2~2~g~2
_19_
m). This structure was then dried in a forced air oven
for approximately three minutes. A secondary film
substrate was applied over the coated web. A sheet of
paper was placed over the laminate to protect it and an
iron set at low heat (surface temperature approx. 150F
(66C)) was run across the paper with mild hand
pressure. Laminates are cut into 1 inch (2.54 cm) width
strips and tested by the T-peel test (ASTM D-1876-72) at
12 inch/min. (30.48 cm/min.). The resulting force was
reported in lbs (force)/inch (kg/cm).
An adhesive system was evaluated by test method
(d) to determine adhesive performance in film to film
laminations. Accordingly, two corona treated
polypropylene films (Mobil Bicor~ 278T) were laminated
by the above procedure. T-peel adhesion results are
contained in Table VI.
Table VI
T-Peel
Adhesive System Adhesion,
(kg/cm)
Sample C 200 (36)
25Example 8 425 (77)
(Sample C/Sample 3*)
* Blended in a 40/60 ratio
(e) Pressure Sensitive Adhesive Test: The
adhesive properties of a candidate pressure sensitive
adhesive were measured according to the Pressure
Sensitive Tape Council (PSTC) Procedure Nos. 1, 5 and 7.
The peel adhesion test involved peeling the tape at a
180 degree angle after application under relatively
heavy pressure. The quick stick test involved peeling
35,635-F -19-
-
.
,
' ' ' :
2~2~
-20-
the tape off at a 90 degree angle after application
under a relatively light pressure. Both tests are
reported as the force required to remove the tape.
Shear adhesion was measured according PSTC No. 7 using a
500 grams (g) mass at 120F (49C). In this test, a
shear force of 2 degree angles was applied in an oven.
The results are reported as the time required for the
bond to fail at a given temperature.
Several adhesive systems were evaluated by test
method (e) to determine pressure sensitive adhesive
properties. Tests were conducted at 72F (22C~.
Results are contained in Table VII.
3o
35,635-F -20-
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-21-
Table VII
Pee1
AdhesiveAdhesion, Quick Stick, Shear
Formulationlbs/in lb /i= (Hours)
Sampl~ D ~ ~ ~ ~1.8 ~0.3)~ 0.8 (0. U>100
Example 9 3.6 (0.6)1.2 (0.2) 80
(Sample D/ Sample
0 3; 60/401 ~:
Comparative 3.6 (0.6)1.4 (0.3) ~ >100
Example II
(Sample
D/Conventional
Tackifier*;
60/40)
Comparative 3.0 (0.5)1.6 (0.3) 25
Example III
(Sample
D/Conventional
Tackifier~*;
60/40)
*Comparative, polystyrene tackifier Piccolastic A-75,
available from Hercules, Inc.
**Comparative, polystyrene tackifier, Piccolastic A-50,
available from Hercules, Inc.
The above results indicate the present
invention is suitable for preparing pressure sensitive
adhesives having good properties.
35,635-F -21-
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