Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
:1~930 ;J~
K 4863
HOT ~I.T SEALZ~NT CCMPOSITIONS
This invention relates to improved adhesives, sealants and
caulking co~pounds. More particularly, it relates to solvent free,
hot melt sealant compositions containing mixtures of hydrogenated
styrenic block copolymers with tackifying resins and reinforcing
resins which yield a sealant composition having improved adhesion
without a primer, creep resistance at elevated temperatures and low
moisture vapour transmission rates, rapid build up in viscosity
with cooling and thixotropic application characteristics.
US patent specification 4,294,733 concerns a sealant system
comprising an adhesive composition and a primer co~position. The
use of a primer provides relatively good adhesion and cohesive
failure in peel tests for adhesion. Both adhesive and primer
composltions involve the use of Kraton G rubber, which has low
moisture transmission rates compared to unsaturated Kraton D rubber
products. "Kraton G" is a trade~rk for block copolymers having two
polystyrene endblocks linked to a substantially saturated polyolefin
rubber midblock. "Kraton D" is a trademark for block copolymers
having two polystyrene endblocks linked to an unsaturated polyolefin
rubber midblock. The adhesive composition has a moisture vapour
transmission rate of not more than about 0.5 g per m~ per day,
measured at 38 C and comprising per hundred parts by weight of the
adhesive composition, from 5 to about 50 parts by weight of the
adhesive copolymer having two polystyrene endblocks linked to a
substantially saturated polyolefin rubber midblock, from about 5 to
about 50 parts by weight of an aliphatic hydrocarbon resin having a
melting point not less than 60 C, from about 2 to about 40 parts
by weight of a curable epoxy resin and a finely divided inorganic
filler, and the primer composition. A primer was needed when using
the Kraton G rubber formulation in order to obtain a sufficiently
strong bond for bonding panes of glass to a spacer assembly. In
some instances, additional heat, pressure and ultraviolet radiation
1~93~
-2- 63293-2769
was required to assure a secure bond.
It is an object of the present invention to provlde a
hot melt sealant composition prepared from a diblock copolymer,
triblock~-diblock copolymer, a triblock copolymer, or mixtures
thereof that is 100~ solids, one component, with a low moisture
vapour transmission rate, high peel adhesion to glass and
aluminium and does not require the use of a primer.
It is a further object of the invention to adjust the
cohesive strength of the sealant by formulating the sealant to a
specific A-B-A/A-B ratio thereby achieving cohesive failure in
peel tests for adhesion while maximizing cohesive strength.
Accordingly, the invention provides a hot melt sealant
composition which comprises-- ~
a. 0 to 50 parts by weight of a multiblock copolymer having
at least two endblocks A and at least one elastomeric
midblock B;
b. 50 to 100 parts by weight of one or more diblock
copolymers consisting of one block A and one block B',
wherein:
the blocks A and A' comprise monoalkenyl arene blocks
and the blocks B and B' comprise substantially
completely hydrogenated con~ugated diene polymer blocks,
and the average molecular weight of the blocks A and A'
is greater than the minimum molecular weight needed to
obtain microphase separation and domain formation of the
blocks A and A', and is less than the maximum molecular
weight which would render the polymer incapable of being
melt processed;
~293~74
-2a 63293-2769
c. 50 to 400 parts by weight of a midblock compatible
component wherein said midblock compatible component
is a resin, plasticizer or mixture thereof, that is
compatible with block B and B', said component present
in a content sufficient to maintain the resultant
composition in a pliable condition at room temperature
and to maintain the glass transition temperature of the
resultant compositlon below 10C; and
d. 0 to 100 parts by weight of an endblock compatible resin
wherein said resin is preferentially compatible with
blocks A
.
.
. .
~Z93(~
and A' and is a coumarone-indene resin, a polystyrene resin, a
vinyltoluene-alphamethylstyrene copolymer or a polyindene
resin.
The average molecular weight of the A and A' blocks are
between 3,000 and 40,000.
The monoalkenyl arene content of the multiblock and diblock
copolymers is no re than the maximum weight per cent needed to
retain a modulus suitable as a sealant in the resultant composition
and no less than the minimum weight per cent needed to obtain the
desired phase separation and the desired cohesive strength. The
average monoalkenyl arene content is between 7% and 45% and preferably
between 10% and 40% by weight. The most preferred weight per cent
is between 10% and 30%, particularly between 15% and 30%. Very good
results have been obtained with said contents being in the range of
from 15~ to 18%.
The hot melt sealant formulations of the instant invention can
also include fillers, pigments, ultraviolet inhibitors, antioxidants,
adhesion promoters and thixotropic agents.
The midblock compatible component can be either a midblock
compatible resin or a midblock ccmpatible plasticizer or mixtures
thereof. When mixtures of midblock compatible components are used,
each may be included in the formulation up to a total of 400 parts
by weight.
The midblock ccmpatible resins may be any of a variety of
hydrocarbon resins, such as hydrogenated rosins, synthetic poly-
terpenes and the like. For optimum heat stability, weatherability
and compatibility, the preferred tackifying resin is a saturated
resin, e.g. a hydrogenated dicyclopentadiene resin or a hydrogenated
polystyrene or polyalphamethylstyrene resin.
m e midblock compatible plasticizer may be rubber extending
plasticizers, or compounding oils or liquid resins. These may be
oils having a high content of saturated compounds or of aromatic
compounds. Naphthenic or paraffinic processing oils having a low
content of aromatic compounds are preferred.
12~3~7~
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The endblock compatible component is used at a content which
is less than the solubility limit of the component in the polymer
with utility to maintain the cohesive qualities of the resultant
co~position at elevated temperatures.
The present invention also includes sealant compositions
comprising combinations of at least one of the group oonsisting of
diblock copolymer, triblock/diblock co~olymer, triblock copolymer,
and mixtures thereof.
Kraton G rubber in solvent based sealants have demonstrated
thermal, oxidative and ultraviolet stability, excellent mechanical
properties at ro~m temperature, high upper service temperature,
good ozone resistance, and resistance to slump at elevated tempera-
tures. Although adequately fulfilling the performance requirements
for some sealants, solvent systems have the disadvantages of
solvent release, long cure time, and shrinkage. A solventless
system has the advantage of low energy consumption, high speed
processing and little or no air pollution. In addition, saturated
Kraton G r~bber is thermally stable during heat processing and
exhibits excellent weatherability in outdoor applications. Kraton G
r~bber based hot melt sealants would have excellent mechanical
properties rivaling silicone but with lower moisture vapour trans-
mission (MVT) rates, the hot melt processing advantages of butyl
hot melts but with better low temperature flexibility and creep
resistance and adhesion comparable to polysulphides but with better
ultraviolet resistance.
The most significant advantage of a hot melt sealant based on
Kraton G r~b~er is hot melt processing. Some of the advantages of
hot melt processing are: (l) simple application, requiring no
mixing or proportioning of reactants, (2) rapid set to a solid
state allowing rapid production rates. Units can be moved and
packaged within minutes after fabrication (3) virtually no waste.
Trim or excess sealant can be reused. In contrast to the inherently
high viscosity of partially crosslinked butyl based hot melt
systems, physical crosslinking Kraton G rubber sealants can be
formulated at lcwer viscosity than butyls. The advantages of high
" 1293~
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speed processing equipment dcvelopment, including melt-on-demand
applicators which reduce the pot-life requirement, reduce the
possibility of thermal degradation.
A one-part, single-seal hot melt sealant based on Kraton G
rubber will have a good balance of properties matching or exceeding
the unique advantages of ccm~ercial sealants. By reinforcing the
domain structure of Kraton G rubber in sealants, formulations can
be developed with the proper balance of properties: high upper
service te~perature without slump or creep, low temperature flexi-
bility and good adhesion to a broad range of substrates and excellent
weatherability inherent to saturated Kraton G rubber.
At elevated temperatures polystyrene damains soften and Kraton
G rubber based campounds can be processed as thermoplastics. Upon
cooling polystyrene domains reform to give outstanding properties
without chemical crosslinking.
Block copolymers with polyisoprene and polybutadiene ~idblock
segments have found a wide variety of applications. Saturated S-I-S
and S-B-S block copolymers, designated S-EP-S and S-EB-S, have
better ultraviolet and therma] stability than their unsaturated
counterparts. Diblock S-EB and S-EP polymers that are weaker than
triblock polymers are also available. By blending d;hlock and
triblock polymers in specific ratios, sealants can bc formulated
with optimum cohesive strength such that the sealant demonstrates
good peel adheslon and fails cohesively in peel.
This composition uses Kraton G rubber of three types: A-B
diblock copolymer, A-B-A/A-B copolymer, and A-B-A triblock copolymer.
The blocks A and A' have average molecular weights ranging from
4,000 to 150,000. The elastameric hydrogenated polyconjugated diene
block B has average molecular weights ranging fram 18,000 to
250,000 and even 500,000. The poly(conjugated diene) block contains
at least 20% of the monomer units polymerized in the 1,2 confi-
guration. Hydrogenation of those blocks is carried out to a point
where at least 95% of the aliphatic double bonds is saturated, and
less than lO per cent of the aromatic double bonds of the poly(alpha-
m~noalkenyl arene) block are hydrogenated.
lZ~3~74
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Blocks A comprise predominantly polymer blocks of at least one
monoalkenyl arene while blocks B comprise predominantly hydrogenated
polymer blocks of at least one conjugated diene.
Blocks A are prepared by block polymerization of such monomers
as styrene and vinyltoluene. Blocks B are prepared by block poly-
merizing conjugated dienes such as butadiene or isoprene and
thereafter hydrogenating the polymer block.
Each block A or A' for a triblock or a diblock copolymer
preferably has a true average molecular weight in the range of from
4,000 to 50,000, more preferably from 7,000 to 40,000 and most
preferably frcm 10,000 to 25,000.
Each B block of the ABA block copolymer is suitably twice the
size of the B' block of the A'B' block copolymer.
For the block B, the true molecular weights are preferably in
the range of 18,000 to 300,000, more preferably in the range of
70,000 to 225,000 and most preferably in the range of 150,000 to
200,000.
For the block B', the true molecular weights are in the range
of 9,000 to 150,000, preferably in the range of from 35,000 to
115,000, and more preferably in the range of 75,000 to 100,000.
These molecular weights are true molecular weights corrected
from styrene equivalent molecular weights from gel permeation
chromotography.
Tackifying resins are blended with the block copolymer to
provide tack. Examples of tackifying resins which may be used in
the compositions accord~ng to the present invention are terpene
resins (Piccohesive 125); polyterpene resins (Wing Tack 95 and
Foral 105~; phenolic resins (SP559 and Super Beckocite 2000);
hydrogenated rosin (Stab lite ester 10); and hydrocarbon resins
(Nevillac 10 and ERJ 683~. Typical plasticizers are polybutylenes
having a m~lecular weight not to exceed about lO,OOO; (Vistanex
LMMS~; phosphate esters (Santicizer 148~; dibutyl phthalate; low
temperature plasticizers such as straight chain aliphatic acid
esters (TP9OB, TP95, TP680); paraffin oils (Sun Par 2100); coal
tars, asphalts; and m iokol~TP95 and T9OB. Chlorinated polyphenyl
~ral~
12~3~74
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;~ (Aroclor 5460~ and chlorinated biphenyl (Aroclor 1254~ may be used
for both their tackifying and plasticizing properties.
More particularly, Regalrez 1018 (Hercules) and ECR 327
(Exxon) are preferably present in the hot melt sealant compositions.
The polymers and tackifying resins are intimately mixed and
blended with plasticizers to lcwer the mcdulus of the sealant and
in some cases, lower the overall cost in making the hot melt
sealant compositions according to the present invention.
Like plasticizers, adhesion promoters, such as organo silanes
or organotitanates can be added to the mixture.
Like plasticizers, adhesion promoters are incorporated in most
compositions in am~unts ranging from 0.5 to 50 parts by weight for
each 100 parts by weight of the elastomer and are preferably epoxy
resins, organo silanes, organotitanates, and mixtures thereof.
Typical adhesion promoters are epoxy resins having an epoxide
equivalent of from 150 to 3000 such as the resins sold by Shell
Chemical Ccmpany under the trade names Epon 1002 and Epon 828~f
Among the organic silanes employed are those sold by Union Carbide
Corporation which are vinyl, cyclic epo ~ , aliphatic e~oxy and
methacryloxy silanes identified as A-186, A-187, A-153 and A-151.
Various kinds of inert fillers can be added to the mixture.
These fillers can include clay, calcium carbonate, talc and the
like. Pigments such as titanium dioxide and carbon blacks may also
be included.
A new type of block copolymer, hereinafter referred to as
Block copolymer 3 having a 30% coupled version of a triblock
blended with uncoupled triblock in a hot melt sealant formulation
has been found to be extremely effective in achieving the objects
of the invention set forth hereinbefore. m e polystyrene domains
are reinforced with an endblock resin, as described hereinbefore,
and the sealant resists slump at elevated t2mperatures. A midblock
tackifying resin provides tack. m e plasticizer which may be
optionally added lowers the m~dulus, and provides a lower cost
overall. The addition of the fillers lowers cost and reduces slump
~<Jcr~Je ~,k
" lZ~3(~74
-- 8 --
in the adhesive. I~le antioxidants and ultraviolet inhibitors/
stabilizers enhance the weatherability and the processing stability
of the novel composition. A crystalline polymer with high melt flow
and lcw molecular weight that forms a third phase but improves
processability and upper service temperature may be included in the
final formulation.
Polymeric compositions described above can provide sealant
compositions which are capable of extrusions as a hot melt and
harden to yield a non-tacky cohesive elastic mass having a desirable
moisture vapour transmission. Moisture vapour transmission rates
(MVTR) as used here, are determined by ASIM method E-96.
A desirable MNrR for the compositions according to the invention
is less than 0.2 g cm per m2 per day, measured at 25 C or less
than 1.0 g cm per m2 per day measured at 38 C.
To produce any of the compositions according to the invention
and to determine the advantages and characteristics of the formu-
lations, the following methods can be followed:
Mix approximately 450 g of test formulation at 177 C for 30
minutes in a Perkin/Elmer hot oil mixer equipped with a sigma blade
mixing head and nitrogen purge. High shear sigma blade mixers or
twin-screw extruders are particularly suited for Kraton G rubber
based sealants which exhibit a non-Newtonian variation of viscosity
with shear rate. The order of addition of ingredients aims for good
mixing in a short amount of time. Preferably if the midblock resin
is added first, agglomeration of polymer to mixer blades can be
avoided. To increase the shearing action solid ingredients can be
added to the mixer at one time.
Tests which can be conducted on the resultant sealant formula-
tion, include Shore A Hardness, Tensile Strength, Elongation at
Break, Tensile Stress MDdulus (ASTM D412), 180 Degree Peel to
glass, aluminium and steel, Slump in a Vertical Channel, Shear
Adhesion Failure Temperature Flexibility. These tests were chosen
to determine mechanical properties of the formulated sealant, the
range of service temperatures and adhesion capability.
`` lZ93~
g
Other tests relevant to field performance include Moisture
Vapour Transmission rate (ASTM E96), Seal Durability of Sealed
Insulating Glass Units (ASTM E773), Frost Point of Sealed Insulating
Glass Units (ASTM E546) and CGSB 12-GP on Insulating Glass Units, a
Canadian Standard.
Samples for testing can be prepared using a "Little Squirt"
(Slautterback Corp. model LS-10) hot melt applicator. Separate
heaters and thermostats for the tank and hose allow the delivery
temperature to be closely controlled at 177 C.
The results of peel adhesion tests for the different for~u-
lations were prepared by heat compression in platens at 130 C and
prepared fram a hot melt gun applicator (Hardman "P" Shooter, Model
240) and set forth in the tables. Application of hot sealants
formulations to cold substrates by the hot melt gun applicator
shawed significantly worse adhesion than sealant formulations
applied by compression under heat. To determine the effect of
substate temperature, tests were conducted on both roam temperature
substrates and substrates heated to 130 C. Hot applied test
formulations onto cold substrates without further heat processing
approximates actual field application and gives good indications of
performance in the field.
The novel sealant formulations contained Kraton rubbers
selected on the basis of low melt viscosity and intermediate
styrene endblock size. Law melt viscosity provided formulating
latitude and good wetting of the substrate. An intermediate size
endblock provided a domain structure large enough to "build-up" the
endblock with endblock reinforcing resins while maintaining moderate
hardness. One Kraton rubber formulation having a 30/70 blend of an
S-EB-S bloc copolymer and an S-EB bloc copolymer was used and is
denoted as block copolymer 2 in the tables hereinafter. Another
Kraton rubber formulation is an S-EB block copolymer, which is half
the molecular weight of the S-EB-S block copolymer and is referred
to as block copolymer 3.
The midblock resin was chosen to keep the rubber midblock
glass transition tem~erature (Tg) as law as possible while
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providing tack. Low temperature flexibility at -30 C to -40 C is
required to prevent cracking or crazing failure of the sealant
during low temperature exposure. Since the polymer midblock Tg is
-58 C, the use of a tackifying resin in large quantities results
in an increase in midblock Tg, leading to embrittlement at lcw
temperatures. The addition of large amounts of Hercules resin
Regalrez 1018 which has a Tg of -24.5 C will not increase Tg to
the extent other resins with higher Tg would. Recently, Exxon resin
ECR 327 has beccme available with a Tg of -35 C. This resin is
claimed to have equivalent stability to Hercules Regalrez resins
but has not been tested.
The endblock resin was chosen on the basis of high Tg and
stability. Hercules resins Kristalex 5140 and Endex 160 have glass
transition temperatures of 86 C and 113 C, respectively. Roth are
crystal clear with excellent thermal and ultraviolet stability.
Both resins were studied for their effect on the upper service
temperature, i.e. resistance to slump and shear at elevated temper-
atures. Studies on clear solvent-based sealants suggest that a
small quantity of endblock resin in a sealant with a sufficiently
large polystyrene endblock size will produce a clear sealant.
Studies for clarity were not conducted.
A high melt flow polypropylene (PP) was included in the
formulation studies to raise the upper service temperature. Isotactic
polypropylene has a melting point temperature of 165 C. In Kraton
rubber compounds, PP can form an interpenetrating network (IPN)
under the proper processing conditions. At service te~peratures
below its melting temperature the PP IPN gives higher upper service
temperatures in the sealant as measured by slump and SAFT.
To improve resistance to thermal, oxidative and ultraviolet
degradation a combination of hindered phenolic antioxidant (Irganox
1010~, benzotriazole ultraviolet inhibitor (Tinuvin P ~and a
hindered amine ultraviolet inhibitor (Tinuvin 770~ are used to
stabilize the formulation against degradation. Tinuvin P and
Irganox 1010 are known to have a synergistic effect in polymer
stabilization.
Q~ D~ ~RK
lZS3(~ 4
- 11 ~
m e effects of endblock resin as compared to PP in upper
service improvement are lower viscosity and modulus, greater
elongation, peel, lap shear and 5AFT than for the same parts per
hundred (phr) of PP. This demonstrates the improvement in properties
that are possible through reinforcement of polystyrene domains
structure in contrast to reinforcement through a third phase.
The use of Endex 160 at 50 phr gives dramatic improvements in
properties. The effect on upper service temperatures is equivalent
to 100 phr of Kristalex 5140 in tensile strength, SAFT, lap shear
and slump. Peel to glass and elongation exceeds that of 100 phr
Kristalex 5140 while hardness and viscosity increase to a lesser
extent. Based on these results Endex 160 is chosen over Kristalex
5140 as the endblock resin.
A high performance insulating glass edge sealant must satisfy
many requirements as discussed in the introduction. Of these
requirements, peel adhesion to cold substrates may be considered a
primary requirement since it affects many critical properties of
the sealant. Once good adhesion to cold substrates is achieved the
proper adjustments in the formulation will lead to a sealant with a
good balance of properties.
The following Examples further illustrate the invention.
The polymers used in the Examples are shown in Tables 1 and 2.
TABLE 1
Polystyrene
Polymer Type Content (%wt) A-B-A/A-B Ratio
Block copol~ner 1 A-B-A Triblock 30 100/0
Block copolymer 2 A-B Diblock 24 0/100
Block copolymer 3 A-B-A/A-B 30 30/70
Block copolymer 4 A-B Diblock 17 0/100
Block copolymer 5 A-B-A/A-B 17 70/30
Block copolymer 6 A-B Diblock 15 0/100
Block copolymer 7 A-B-A/A-B 15 60/40
Block copolymer 8 A-B Diblock 30 0/100
1~93(~'74
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TABLE 2
Polymer Type Molecular Wt.
Block copolymer 1 A-B-A Triblock 7,000-35,000-7,000
Block copolymer 2 A-B Diblock 40,000-105,000
Block copolymer 3 A-B-A/A-B 7,000-35,000-7,000/7,000-17,000
Block copolymer 4 A-B Diblock 11,000-57,000
Block copolymer 5 A-B-A/A-B 11,000-114,000-11,000/11,000-57,000
Block copolymer 6 A-B Diblock 15,000-85,000
Block copolymer 7 A-B-A/A-B 15,000-170,000-15,000/15,000-85,000
Block copolymer 8 A-B Diblock 7,000-17,000
m ese polymPrs noted hereinbefore are one of three types:
A-B-A triblock, A-B diblock or A-B-A/A-B triblock/diblock copolymers
where A is polystyrene and B is hydrogenated polybutadiene or
polyisoprene. m ese polymers may be used in hot melt sealant
formulations alone or in various combinations to yield a final hot
meit sealant formulation containing a specific A-B-A/A-B ratio.
When A-B, A-B-A/A-B, and A-B-A type block copolymers are used alone
or in co~bination for the purpose of achieving low cohesive strength
in the hot melt sealant, there are six difference classes that
provide a low A-B-A/A-B ratio and increase the possibility of
cohesive failure in peel tests for adhesion; these classes include:-
Class l: A-B diblock copolymer
Class 2: A-B-A/A-B block copolymer
Class 3: A-B diblock copolymer and A-B-A triblock copolymer
Class 4: A-B-A/A-B block copolymer and A-B diblock copolymer
Class 5: A-B-A/A-B block copolymer and A-B-A triblock copolymer
Class 6: A-B-AJA-B block copolymer, A-B diblock copolymer and
A-B-A triblock copolymer.
Block copolymer 1, an A-B-A triblock copolymer, is included to
demonstrate conventional prior art technology. Block copolymers 2
throu~h 8 are high molecular weight polymers that pr w ide a balance
of properties such as improved high temperature creep resistance,
good adhesion, and thixotropic application characteristics.
12~3~4
- 13 -
Example 1
Table 3 compares the water vapour transmission rate of unsat-
urated S-B-S or S-I-S polymers such as Kraton D formulations to
block copolymer 1 being an S-EB-S polymer in which the EB block is
substantially completely hydrogenated. ~ested under standard
testing condition of 37.8 C and 90% relative humidity, hydrogenated
S-EB-S block copolymer 1 allows less water vapour to permeate than
unsaturated S-I-S or S-B-S polymers. In the novel sealant appli-
cations where the sealant must provide a barrier function to
moisture penetration, these hydrogenated block copolymers are
preferred over Kraton D block copolymers.
TABLE 3
Water Vapour Transmissions Rates
of Block Copolymers
g cm per m2 per day
Block copolymer SBS 1.07
Block copolymer SIS 0.871
Block copolymer l 0.35
Example 2
The effect of an A-B diblock copolymer in an A-B-A/A-B polymer
such as block copolymer 3 is illustrated in Table 4. The tensile
strength of block copolymer 3 is 2.41 MPa at break where as the
tensile strength at break of block copolymer 1 is 31.0 MPa. Hot
melt sealants formulated with Kraton Formulation A are high in
cohesive strength and will not fail cohesively in peel tests for
adhesion without a primer.
`` lZ93~4
- 14 -
TABT~ 4
Com~arative Properties of Thenmoplastic Rubkers
Block Copolymer 1 Block Copolymer 3
Tensile strength at 31.0 2.41
break, (MPa)
300~ Modulus, (MPa) 4.83 __
Elongation at Break (~) 500 200
Example 3
me effect of adjusting the A-B-A/A-B ratio is illustrated in
Table 5. By blending block copolymer 1 with block copolymer 3, the
A-B-A/A-B ratio in the sealant formulation is increased from 30/70,
50/50, to 70/30 in formulations A, B, and C respectively. The
effect of a higher A-B-A/A-B ratio is to increase tensile strength,
elongation, modulus and hardness. Additionally, a higher ratio of
A-B-A/A-B so~iwhat improves the upper service temperature properties
such as slump and SAFT. At high A-B-A/A-B ratios, however, the mcde
of adhesion failure to glass becomes adhesive failure to the glass
substrate resulting from the high cohesive strength of the sealant.
Test results in Table 5 show the effect of coupling efficiency on
performance. A monotonic increase in m~duli, tensile strength and
elongation i5 observed. Melt viscosity, hardness, lap shear and
degree of slump at elevated temperatures also correlate directly
with coupling efficiency showing an increase with higher coupling
efficiency. These results are expected from the stronger network
for higher triblock content Kraton rubber.
Peel results show greater variability with substrate. Maximum
adhesion to glass is at 50% coupling efficiency while maxim~m
adhesion to aluminium and steel is at 70% coupling efficiency. The
mechanism of failure in peel tests is critical in determining the
significance of the peel value. Cohesive failure with a high kN per
m value is the most desirable while adhesive failure to substrate
indicates poor adhesion and high cohesive strength of the polymer.
1293(~74
Coupling efficiency of the polymer in the range of 50-70% will give
high peel values to glass and the mode of failure was oohesive for
both glass and aluminium.
Similar results are found in Table 6, where the addition of an
A-B diblock copolymer, block co~olymer 8 in a 50/50, A-B-A/A-B
weight ratio with block copolymer 1 provides improved adhesion in
sealant D compared to sealant E consisting of 100 parts by weight
A-B-A triblock, block copolymer 1.
~29313'74
- 16 -
TABLE 5
Formulation A B C
-
Block eopolymer 1 0 30 57
Block eopolymer 3 100 70 43
Midblock Resin tRegalrez 1018)a 270 270 270
Endbloek Resin (Endex 160)a 54 54 54
Polypropylene (Shell DX 5088)b 18 18 18
Stabilizer (Irganox 1010)
Stabilizer (Tinuvin 770)c
Stabilizer (Tinuvin p)c 1.5 1.5 1.5
A-B-A/A-B 30/70 50/50 70/30
Class 2 5 5
Properties
Tensile strength (MPa) 0.41 0.69 0.72
Elongation (~) 425 550 675
lO0~ Modulus (MPa) 0.23 0.24 0.30
Hardness ~Shore A) 26 27 37
Melt Viscosity (Pa.s)d 1.040 1.780 3.055
180 Peel to Glass (kN per m)e 3.3C 6.8C 3.0AS
SAFT (C) 54 54 64
Slump (C) 65 65 70
a) Produet from Hereules Ine.
b) Produet from Shell Chemieal Co.
e) Product from Ciba Geigy
d) At 177 C
e) C: cohesive failure
AS: adhesive failure
f) Shear adhesion failure temperature
.
1~3~
- 17 -
TABLE 6
Formulation D E
Block Copolymer 1 50 100
Block Copolymer 8 50 0
Midblock Resin (Regalrez 1018) 250 250
Endblock Resin (Kristalex 5140) 50 50
Stabilizer (Irganox lO10)
Stabilizer (Tinuvin 770)
Stabilizer (Tinuvin P) 1.5 1.5
A-B-A/A-B Ratio 50/50100/0
Class 3 __
Properties
Hardness (Shore A) 22 32
180 Peel to Steel (kN per m) 3O3 1.6
Melt Viscosity (Pa.s) 0.8002.200
Example 4
Table 7 compares the prcperties of three hot melt sealants
formulated by combining polymers to achieve an A-B-A/A-B ratio of
50/50. me other sealant ingredients are identical in all three
~onmulations. In successive formulations from F to H, the sealants
possess improved strength and more importantly better high tempera-
ture characteristics. me Experimental Kraton G polymers also
provide the desired application viscosity for a hot melt insulated
glass edge sealant.
~Z~3~'74
- 18 -
TABLE 7
Formulation _ G H_
Block copolymer 1 30 0 0
Block copolymer 3 70 0 0
Block copolymer 4 0 28 0
Block copolymer 5 0 72 0
Block copolymer 6 0 0 21
Block copolymer 7 0 0 79
Regalrez 1018 270 270 270
Endex 160 71 71 71
Tinuvin P 1.5 1.5 1.5
Tinuvin 770
Irganox 1010
S-EB/S-EB-S Ratio 50/50 50/50 50/50
Class 5 4 4
Properties
Tensile Strength (MPa) 0.94 2.65 3.15
Elongation (%) 590 1280 1300
Modulus, 100~ (MPa) 0.28 0.15 0.19
Hardness, Shore A 32 16 15
Melt Viscositya, (Pa.s) 1.090 71.467 --
Peel to Glass (kN per m)b5.6PC 7.4 9.6
Peel to Glass/Soak (kN per m)3.7 1.2 --
Peel to Aluminium (kN per m)2.1 3.3 4.2
SAFT (C) 59 72 84
Slump (C) 65 110 150
a) measured at 177 C
b) PC = partial cohesive failure
1~3C~'74
-- 19 --
E~ample 5
Sealants in Table 8 are formulated to low A-B-A/A-B ratios
that give cohesive failure in peel tests for adhesion while maximizing
tensile strength. This table illustrates the use of various ingre-
dients that promote the final properties of the sealant such ascoupling agents, fillers, carbon black and terpene phenolic resin.
m e formulation can be compared to the properties of a cammercially
available hot melt butyl sealant (formulation Q).
1293(i'74
- 20 -
TABLE 8
Formulation _ J K L M N O P Q_
Block copolymer 1
Block copolymer 2 33 33 33 0
Block copolymer 3 5 5 5 5 5
Block copolymer 4 72 35 35
Block copolymer 5 28 27 27
Block copolymer 6 100 68 33 66 66
Block copolymer 7 32 29 29
Midblock Resin 270 270 270 250250 250 250 250
(Regalrez 1018)
Endblock Resin 71 71 71 50 50 50 50 50
(Endex 160)
Polar Resin 50
(Super Nirez 6040)
Stabilizer
(Irganox 1010)
Stabilizer
(Tinuvin 770)
Stabilizer 1.5 1.5 1.5 1.51.5 1.5 1.5 1.5
(Tinuvin P)
Filler (Calcium 100
Carbonate)
Coupling agent 1 4.5
(A-1120)
Coupling agent 2 2
(LICA-09)
Pigment (carbon 5 5
black)
A-B-A/A-B Ratio 0/10020/80 20/80 20/80 20/80 20/80 20/80 20/80
Class 1 4 4 6 6 6 6 6
` 1;~93(:17~
Formulation I J K L M N O P Q
Properties
Tensile strength 0.300.41 0.91 0.39 0.620.64 0.85 1.03 0.01
(MPa)
Elongation (%)1050 10801000 863 600 10501400 1467 1300
100% Modulus IMPa) 0.130.11 0.26 0.12 0.300.25 0.12 0.23 0.21
Hardness (Shore A) 16 15 15 17 24 15 13 28 45
Melt Index 1152 -- 549 319 209 254 391 1116 207
(g/10 m m)
180 Peel to Glassa 5.6C 6.3C 14.0PC 9.6C 9.6 10.5PC13.1C 10.7C 3.0C
(kN per m)
180 Peel to Glass/ 07.9C 0 0 4.6 0.5 0.7 -- 2.6C
soak (kN per m)
180 Peel to Alumi- 6.1C3.7 6.6 8.2C 7.0 5.8 6.7 13.1C 3.5C
nium (kN per m)
SAFT (C) 64 61 76 69 77 77 73 67 60
Slump (C) 130 75 145 185 195 145 150 105 210
a) PC = partial cohesive failure
Example 6
The moisture vapour transmission rate of the Kraton G polymer
is affected by the selection of ingredients. Table 9 illustrates
the effect of a midblock compatible resin, an endblock compatible
resin and polyisobutylene (Vistanex I~S, Exxon), a low moisture
vapour transmission rate polymer. When properly formulated, Kraton
G block copolymer based hot melt sealants (formulations B and M)
are as effective as a commercial hot melt butyl sealant (formula-
tion Q) in providing a barrier to moisture vapour transmission.
lZ~33C~
- 22 -
TABLE 9
Moisture Vapour Transmission Rates
Condition
23 C, 50% R.H. 37.7 C, 90% R.H.
g cm per m2 ~er dayl g cm per m2 per day
Block copolymer 1 0.42 (1.4) 1.97 (1.4)
Block copolymer 2 0.19 (1.6) 1.67 (1.6)
Regalrez 1018 200 PHR
Block copolymer 2 0.37 (1.4) 2.46 (1.4)
Endex 160 50 PHR
Block copolymer 2
Vistanex LM-MS 50 PHR 0.23 (1.4) 1.04 (1.4)
Formulation B 0.93 (0.51)
Formulation M 0.25 (1.5)
Formulation Q 0.22 (1.4) 1.03 (1.4)
1) the thickness in mm of the test piece is stated between
brackets
2) R.H. means relative humidity
PHR means parts per hundred
