Note: Descriptions are shown in the official language in which they were submitted.
~5~
BACKGROVND-OF THE INVENTION
1 Field of the Invention
-
This invention relates to an adhesive composition contain-
ing a styrene-butadiene radial block copolymer,a styrene-isoprene
block copolymer, an isoprene-piperylene copolymer and an organic
solvent or mixtures of organic solvents.
2 Descri tion of the Prior Art
P
Contact cements having a relatively high tack time that
are known today are generally based on polychloroprenes, which
require the use of metallic oxides as stabilizers and the use of
pre-milling and prereaction with phenolic resin to provide the
desired properties. However, often these oxides have the tendency
to settle out of the adhesive, necessitating stirring of the
adhesive prior to use. The adhesive herein is capable of per-
forming as a contact cement, however, devoid of any metallic
oxide and which requires no premastication or premilling.
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`` lU54Z~l
SUMM~RY OF THE INVENTION
This invention relates to an adhesive composition pOS5-
essing a relatively high tack time (at least about seven minutes,
preferably from about 10 to about 60 minutes) and an excellent
dead load hot strength (1000-gram dead load of at least about 95 C.,
preferably about 110 C. to about 150 C.), consisting essentially
of a styrene-butadiene radial block copolymer, a styrene-isoprene
block copolymer, an isoprene-piperylene copolymer and an organic
solvent or mixtures of organic solvents.
The styrene-butadiene radial block copolymers present in
the adhesive composition of the present invention are composed of
styrene and butadiene and have at least three long block copolymer
branches radiating from a nucleus. These polymers have the follow-
ing general configuration:
(A - B)XY ,
wherein each terminal A is a styrene polymer, B is a butadiene
polymer, Y is a group derived from a polyfunctional compound having
at least three reactive ~ites and x is-an integer ranging from 3
to 5, but preferably is 3. The amount of styrene present in the
radial block copolymer will range from about five to about 60 weight
per cent, preferably from about 10 to about 50 weight per cent, based
on the weight of the radial block copolymer, while the amount of
butadiene from about 40 to about 95 weight per cent, preferably from
about 50 to about 90 weight per cent, based on the weight of the
radial block copolymer. The Y group which forms the nucleus from
which the polymer blocks radiate is derived from a polyfunctional
compound having at least three reactive sites capable of reacting
with a carbon-lithium bond. Types of polyfunctional compounds which
can be used include the polyepoxides, polyisocyanates, polyimines,
polyaldehydes, polyketones, polyanhydrides, polyesters, polyhalides,
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etc. The styrene-butadiene radial block copolymers used herein can
be made in any conventional manner. A particularly attractive pro-
cedure for making the same is described in U.S. Patent No. 3,281,383
to Zelinski et al.
The styrene-isoprene block copolymer present in the adhe-
sive composition of the present invention has the following general
configuration:
Al - Bl Al
wherein each terminal Al is a styrene polymer block with a glass
transition temperature above about room temperature (26 C.) and
which is relatively incompatible with the elastomeric segment s1,
defined hereinafter, with the average molecular weight of each A,
being from about 2,000 to about 100,000, preferably from about 5,000
to about 50,000. Bl is an isoprene polymer with a glass transition
temperature below about room temperature (26 C.), with the average
molecular weight of Bl being from about 25,000 to a~out 1,000,000,
preferably from about 50,000 to about 500,000. The difference in
glass transition temperature between an end block A, and a center
block B, is preferably greater than about 100 C. In the block
copolymer used herein the total of the terminal blocks Al will
amount to about eight to about 50 weight per cent, preferably about
10 to about 40 weight per cent, based on the total weight of the
block copolymer.
The third component of the adhesive herein is an isoprene-
piperylene copolymer. These copolymers can be obtained, for example,
by polymerization of a C5 stream of aliphatic petroleum derivatives
containing a major porportion of piperylene and isoprene monomers,
for example, as in U.S.Patent No. 3,290,275 issued December 6,1966
to Velsicol Chemical Corporation. Although the stream being poly-
merized can contain small amounts of higher carbon numbermonomers, the character of the stream is essentially that attribu-
:a~le to its C5 components. The stream can contain, for example,
~A
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abo~t 2S weight per cent each of piperylene and isoprene, with the
remainder including, for example, tertiary amylenes, tertiary
monomers, such as styrene or beta pinene, etc. but the copolymer
wiIl be made up mainly of piperylene and isoprene. In general,
the melting points of these copolymers are in the range of about
70 to about 130 C.
The last component required herein is an aliphatic, aro-
matic, ester, ketone or chlorinated solvent or mixtures thereof
boiling between about 35 to about 145 C., preferably between about
38 to about 140C., at atmospheric pressure. Those boiling below
the defined range will be released too rapidly from the adhesive
composition, causing handling problems,such as insufficient working
time, while those boiling above the defined range may require a-
longer time than normal time for the adhesive to set. Solvents
which can be used are aromatics having from six to eight carbon atoms,
such as toluene, the xylenes, etc.; aliphatics having from six to
eight carbon atoms, such as normal hexane, normal octane, etc.,
ketones having from two to four carbon atoms, such as methyl ethyl
- ketone, acetone, etc.; esters having from two to four carbon atoms,
~ `
such as ethyl acetate, butyl acetate, etc.; chlorinated solvents,
such as l,l,l-trichloroethane, methylene chloride, etc.
The adhesive composition can be prepared in any conven-
tional manner. For example, the ingredients can be added to the
solvent in any order, after which mixing can take place until a
substantially homogeneous mixture is obtained. Such mixing can be
carried out at room temperature and room pressure over a period of
about one to about four hours, or, alternatively, the ingredients
can be mixed and set aside for about 24 hours during which dissolu-
tion of the various adhesive components takes place.
The adhesive composition herein will consist essentially
of the following components within the following ranges, assuming
1054281
the presence of 100 parts by weight of the styrene-butadiene radial
component in the final composition:
Parts By Weight d
Broad Preferre
Component Range Range
Styrene-Isoprene
Block Copolymer 5-300 20-100
Isoprene-Piperylene
Copolymer 5-300 20-100
Solvent 50-4000 200-800
If desired, a coumarone-indene resin can be added to the
adhesive composition defined above to further improve the dead
load hot strength thereof, although the tack time of the adhesive
composition, as a result of such addition, will be reduced thereby.
If a coumarone-indene resin is added to the adhesive composition,
the amount added must be within a range of about five to about 200
weight per cent, preferably about 75 to about 150 weight per cent,
based on the isoprene-piperylene copolymer. In addition, an anti-
oxidant, such as 1,3,5-trimethyl-2,4,6-(3,5-ditertiarybutyl-4-
hydroxybenzyl)benzene, can be incorporated in the adhesive compo-
sition in an amount of about 0.1 to about five weight per cent,
based on the weight of the final composition.
The new adhesive composition of this invention is particu-
larly useful in bonding wood, plastic, metal, a cellulosic material,
such as paper, glass, etc., to itself or to another member of such
group.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The improved adhesive composition of this invention can
be further understood by reference to the following. Compositions
were prepared using combinations of a styrene-butadiene radial block
copolymer, a styrene-isoprene block copolymer, an isoprene-
piperylene copolymer, a coumarone-indene resin, the antioxidants
1054Z81
1,3,5-trimethyl-2,4,6-(3,5-ditertiary-4-hydroxybenzyl)benzene and
dilauryl thio dipropionate and a solvent (containing toluene,hexane
an acetone in a weight ratio of 1:1:1). Whichever component~ were
used in preparing the compositions were added to the solvent and
the resultant composition was mixed for about one to about four
hours at atmospheric pressure and atmospheric temperature until a
homogeneous composition was obtained. The compositions were then
tested for tack time and for their dead load hot strength as follows:
Tack Time: Wet films of the test adhesives were applied to both
glass and 50-pound Kraft paper with a 10 mil drawn-down bar. At
two-minute intervals l/2-inch strips of the coated paper were cut
and laid film side down on the coated glass. These strips were
applied using moderate finger-tip pressure and were stripped off
immediately after they were applied. The time which had elapsed
between the initial application of the wet adhesive to the two
- substrates and the final drying of the adhesive to the point where
the coated paper no longer adhered to the coated paper were recorded
as tack time.
Dead Load Hot Strength: This test is designed to measure the~ -
resistance of an adhesive to flow under a sustained load (creep)
at an elevated temperature. A canvas-to-steel shear specimen
having a one square inch bonded area was prepared for each test
adhesive. In preparing the specimen two coats of adhesive were
applied to the canvas and one coat was applied to the steel surface.
The coated surfaces were assembled while still tacky and pressed
together with a ten-pound roller. The specimens were aged for one
week at room temperature before testing. The specimen was tested
by suspending it in an oven at 54.5 C. at a constant shear load of
1000 grams. The test assembly consisted of a series of clamps
attached to the top of the oven; the steel portions of the specimen
wa~ secured by these clamps, and the 1000-gram load was then hooked
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into slot-~ which were cut into the canvas portions of the specimen.
The specimen was clamped in a vertical position 90 as to maintain
a shear load on the adhesive joints. The oven temperature was
increased 5.5 C. every 15 minutes until the bond failed or until
a temperature of 150 C. wa~ reached. The temperature at failure
was recorded as the dead load hot strength.
The data obtained are tabulated below in Tables I, II
and III.
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--10--
Referring to th~ components used in the adhesive compo-
sitions above, Solprene 406 is a styrene-butadiene radial block
copolymer made and sold by Phillip~ Petroleum Company and has a
molecular weight of about 250,000 and a butadiene ta styrene weight
ratio of about 60/40. Solprene 411 is a 9imilar radial block:
copolymer of styrene and butadiene, with a molecular weight of about
300,000 and a butadiene to styrene weight ratio of about 70/30.
Kraton 1107 is a styrene-isoprene block copolymer made and sold by
Shell Chemicals wherein the terminal styrene block has a molecular
weight of about 2,000 to about 100,000 and the center isoprene
block has a molecular weight of about 25,000 to about 1,000,000 with
the styrene block constituting about 15 per cent by weight of the
total block. Cumar LX-509 is a coumarone-indene resin made and
sold by Neville Chemicals Company having a melting point of 155 C.
and Sta-tac 100 is an iQoprene-piperylene copolymer made and sold
by Rheichold Chemicals, Inc. having a melting point of 105 C.
The data in the above Tables illustrate the effectiveness
of the improved adhesive compositions of the present invention.
Note in Table I that the improved composition must contain a styrene-
butadiene radial block copolymer, a styrene-isoprene block copolymer,
an isoprene-piperylene copolymer and a solvent. In Runs Nos. II
and III where an isoprene-piperylene copolymer or a styrene-isoprene
block copolymer, respectively, were not present, a tack time of less
than seven minutes was obtained. In Run No. I wherein all of the
necessary components were present, the tack time was higher. The
addition of a coumarone-indene resin to the desired composition of
Run No. IV reduced the tack time but increased the dead load strength
obtained in Run No. I. That a coumarone-indene resin, when added
to the composition herein in selected amounts, wi}l further increase
the dead load hot strength of the composition, is apparent from the
data in Run No. V. The utilization of another styrene-butadiene
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radial block copolymer in Table II and of another solvent in
Table III resulted in compositions having characteristics similar
to those obtained in Table I.
Obviously, many.modifïcations and variations of the inven-
tion, a~ hereinabove set forth, can be made without departing from
the spirit and scope thereof and, thereforej only such limitations
should be imposed as are indicated in the appended claims.
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