Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
l Rubbery Polymer Compositions with Improved Adhesion
The present invention relates to a process ~or producing
rubbery polymer compositions, particularly but not exclusively
those based on butyl polymers, which have improved adhesion
to mineral substrates such as glass and metals. In particular
the invention relates ~ product compositions which may be
used as sealants in double glazing.
Currently sulphonated rubbers are generally supplied as
solutions which need drying and furthermore they tend
to be decomposed by moisture which can come from condensation.
Thus it is desirable to provide an adhesive or sealant
composition that can be applied by ext^rusion and which has
improved resistance to moi~ure.
It is well known that it is difficult to achieve good
adhesion between mineral substrates such as glass and
metals, and rubbery polymers such as butyl polymers including
halobutyl polymers such as chlorobutyl rubber and bromobutyl
rubber. Some commercial adhesives are available for bonding
butyl polymers to substrates, but these have been found to
20be uns~1itable for certain applications. For example,
~nited States Patent 3,366,612 relates to the rendering of
halogen containing polymers such as chlorinated butyl rubber
adhesive to substrates such as glass or metal by reacting
them with a silane. It has been found that although this
method improves the adhesion, it does not result in adequate
adhesion for certain applications.
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1 In accordance with Ur-~ited States Patents 4073776 and 4073826,
the reaction products of novolac resins with various
epoxides are used as tackifiers for elastomers such as
chlorobutyl, however there is no sugyestion also to use
silanes in such compositions.
It has been proposed to use combinations of amino silanes
with epoxy compc,unds as adhesion promoters in a variety of
systems. For example United States Patent 3,850,872 relates
to the use of epoxy compounds and resins, along with
lo amino silanes, to improve glass fibre-elastomer adhesion.
In particular in this patent document the elastomer is
blended with an oily epoxy compound and then compounded with
silane treated glass fibres.
The previously proposed techniques for improving the adhesion
between rubbers and mineral substrates have proved unsatisfactory
where ~s is particularly important that the bond be water
resistant such as with butyl sealants for double glazing.
We have now found that significantly improved adhesion may
be achieved if a rubbery polymer such as a halobutyl rubber
20 is subjected to a stepwise reaction sequence in wh-ch it is
first reacted with a silane, the silane containing rubber
is subsequently mixed with an epoxy resin, and this product
then reacted with further silane.
863~
1 Accordingly the present invention provides a process for
producing a composition having improved adhesion to mineral
substrates characterised in that it comprises in a first stage
reacting a rubbery polymer with a reactive silane (as hereinafter
defined) at elevated temperature; in a se~ond stage mixing the
product of the first stage with an epoxy resin as wetting agent;
and in a third stage reacting the epoxy containing product of
the second st~age with a f~rther amount of a reactive silane
(as hereinafter defined) to form the desired composition.
10 The scope of the invention, it will be appreciated, also
extends to the compositions produced by the defined process,
and to their use as a mastic or a component of a mastic.
.~oreover the invention includes glazing systems which
incorporate such compositions or mastics as sealants.
The term reactive silane as used herein is meant to include
silanes having a first group attached directly or indirectly
to the silicon atom which is reactable with the rubbery
~olymer, and at least one other group attached directly or
indirectly to the silicon atom which is hydrolysable and
20 which, on hydrolysis in contact with the surface of a
mineral substrate such as glass, concrete or metal will give
a strong bond thereto~
.. . . .
1 The reactive silane used in the first reaction stage is
preferably the same as that used in the third stage, althouyh
they may be different if required. The silane may be for
example a mercapto-, epoxy~ or vinyl-silane in which the
specified functiona] groups react with the rubbery polymer,
in the presence of free radical initiator if necess~ry.
However it is particularly preferred that the reactive
silane used is an amino silane such as the commercially
available product Z-6020, N-beta-(aminoethyl) gamma~amino
propyl trimethoxy silane.
The amount of reactive silane used in the first stage of the
process is preferably from 50 to 100%, more preferably from
60 to 75~ of that stoichometrically re~uired to combine with
the rubbery polymer. For example some two thirds of the
stoichometric amount may be used in order to avoid the
reticulation which could take place under certain conditions
if the stoichiometric amount or more is employed.
The rubbery polymer used in accordance with the invention
may be for example EPR, EPDM or an EV~ copolymer. However
20the process has been found to be particularly useful when
the rubbery polymer is a halobutyl rubber such as chlorobutyl
rubber. Bromobutyl rubbers may also be employed, but they
~nera' ly tend to be too react vc for convenience.
1 In the case where the reactive silane is an amino silane
and the rubbery polymer is chlorobutyl rL~bber, the first
staye reaction between the amino grouping and the alkyl
chloride of the chlorinated butyl is believed to proceed by
N-alkylation or the formation of a quaternary ammonium salt,
as set out in ~he following reaction schemes:
p- G~ f H~ )3 - ,- p~ R- s~--(R')3 t H C~
P CL fl~ R~ R'J ~ p_ ~ ~R
P- ce ~ ~--R- S~ )7, ~ R~ ~ R
k~" C,~
In the above, P represents a polymer; R represents a divalent
radical such as an alkylene group eg propylene; R" and R"',
which may be the same or different, represents a monovalent
radical such as an alkyl group e.g. methyl or ethyl; and the
silicon substituents R' may independently be hydrogen
or a hydrolyzable radical with the proviso that at least one
20 R' must be hydrolyzable. By way of example the hydrolyzable
radical may be acetoxy, halo~en, or alkoxy having from 1 to
20, preferably 1 to 10 and most preferably 1 to 3 carbon
atoms. Amino trialkoxy silanes of the formula
NH2~CH2)n Si~ORiV~3 where Riv is alkyl ~nd
'- ~
--6--
l ~ is a number from 1 to 8 have been found to be particularly
useful as reactive silanes in the process of the invention,
especially when the rubbery polymer is chlorobutyl rubber.
A particularly preferred embodiment of the invention therefore
provides a process for producing a composition having improved
adhesion to mineral substrates characterised in that in a
first stage a chlorobutyl rubber is mixed with an aminosilane
having at least one hydrolyzable radical attached to the silicon
atom; in a second stage the product of the first stage is mixed
:Lo with an epoxy resin; and in a third stage epoxy containing product
of the second stage is mixed with a further amount of an
aminosilane having at least one hydrolyzable radical attached
to the silicon atom, to form the desired composition.
Generally with respect to the silane, the primary amine
is preferred. Also, as stated previously, at least one of
the groups on the silane atom should be readily hydrolyzable,
but it is preferred that three of these be hydrolyzableO
The amounts of functional silane to be used will vary to
some extent depending on the degree of hydrolyzable silane
20 functionality required to produce a vulcanized network.
The reactive silane e.g. amino silane is reacted with
the rubbery polymer eg chlorobutyl rubber during the normal
compounding conditions for the rubber; for example reaction
may be achieved by incorporating the silane into the compounding,
at elevated temperatur~s of from 135 to 150C, say at 140C
for about half an hour.
::
... . _ , , .
~ny epoxy resin may be usecl in the second stage of the process.
It is preferred however to use epoxy compounds derived from bis-
phenols and epichlorhydrin, those sold under the Registered Trade
Mark "Epikote", e.g. Epikote 1007, being particularly preferred.
The epoxy resin may conveniently be mixed with the silane treated
rubber with heating, ag2ain preferably at temperatures in the range
135 to 150C.
The epoxy resin serves as a wetting agent with regard to
the rubber polymer, and so to an extent the amount incorporated is
arbitrary. However it has been found that added amounts of 10 to
50 wt %, partic~llarly 25 wt ~, based on the weight of rubbery
polymer are effective.
The second charge of silane may then be reacted with the
epoxy treated material in the third process stage, if required
under similar conditions to those used for the first process stage.
The amount of silane used is preferably at least that stoichiome-
trically required to combine with the epoxy groups present. The
use o an excess amount of silane is even preferred since this will
enhance the formation of chemical bonding between the rubber and the
substrate.
We have found that the compositions produced according to
the present invention have significantly improved adhesion to
mineral substrates, particularly when the modified rubber is chloro-
butyl rubber, compared with unmodified butyl rubbersO On contact
between the substrate and the composition, the alkoxy groups or
other hydrolyzable groups pxesent in the silane attached to the
polymer chains will be
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1 hydrolyzed by traces of water on the mineral s~bstrate
surface to give a strong bond thereto. Frequently in the
use of such compositions there will be sufficient water
present to give a strong bond but if necessary the surface
may be deliberately wetted. It is believed that through
the effect of moisture the alkoxysilane or other hydrolyzable
groups form silanols which can react both among themselves
(thus crosslinking the rubbery polymer and the epoxy resin)
and with e.g. OH groups on the glass surface. The adhesion
can be developed under normal atmospheric conditions or at
elevated temperatures or by immersing the surfaces to be
bonded in hot water~ The compositions are particularly
useful in bonding glass, especially as sealants for double
glazing. It is believed that the presence of the epoxy
resin improves the extent to which the glass is wetted by
the rubber, and that the process technique gives improved
internal bonding and adhesion. It has also been found that
the compositions such as are exemplified hereinafter undergo
crosslinking with time at room temperature. Thus once
20 applled the composition will provide increasingly cohesive
strength.
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1 The compositions, especially modified chlorobutyl rubbers
produced by the process of the present invention are particu-
larly useful as sealants for double ylazing between the
glass and the metal, generally aluminium , spacer. The
compositions will generally be used as a component in a hot
flow mastic which may contain other conventional components
such as polyisobutylene and petroleum resin tackifiers;
fillers such as carbon black and whiting; and other additives
such as stabilisers, antioxidants and pigments. Thus in one
lo embodiment the process of the invention includes incorporating
a filler or other conventional additive at any stage. By
way of example the final composition may have the overall
ingredients, based on the composition or as whole, of
7.5-12.5~ rubbery polymer; 2-5~ epoxy resin; 0.5-1.5%
silane: 15-20% polyisobutylene; 10-15% carbon black; 25-30
whiting; 25-30~ plasticiser/tackifier. The handling and
service properties (tem~perature and viscosities) of such
compositions may be adjusted by controlling the ratio of
rubbery polymer and additive e.g. polyisobutylene, or by
20 controlling the molecular weight of the polyisobutylene.
The mastic may then be extruded at elevated temperatures
between the surfaces to be adhered. The temperatures vary,
depending on the viscosity of the mastic composition and may
be in the range 150-180C. -Alternatively the composition
may be in the form of a tape.
The following Examples illustrate, but in no way limit,
the invention.
.
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1 Example 1
A rubber composition in the form of a mastic was prepared
by mixing the components in the manner described below,
the composition having the ingredients in the proportions
(parts by weight)indicated in Table 1 in which:~
Chlorobutyl 1068 is a chlorobutyl rubber; Vistanex MML-140
is a polyisobutylene of molecular weight 1900 000 - 2350
Q00; Vistanex LM-MS is a ~clyisobutylene (molecular weight
about 55000); silane Z-6020 is commercially available
10 N-beta-~aminoethyl) gamma-amino propyl trimethoxy silane;
Epikote 1007 is a solid bisphenol A-epichlorohydrin epoxide
resin; Omya BL is a whiting; Escorez 1304 is a petroleum
resin tackifier, and FEF ls a carbon black.
Thus 40 parts of chlorobutyl rubber and 20 parts of car~on
black were mixed in a Banbury internal mixer at 140C to
make a masterbatch. Half of this masterbatch was placed in
a kneader mixer at 110'~C with 30 parts polyisobu~ylene and
15 parts car~n black and after 15 minutes mixing the
remainder of the masterbatch~ the remainder of the polyisobu-
~o tyiene and the remainder of the carbon black were added.
Afte-f a further 15 minutes mixing 33.33 parts tackifier and
50 parts whitiny were added and mixing was continued for
another 15 minute period. Thereafter the remainder of the
tackif~er and whiting was added and the temperature was
~D~
. .
increased with mixing over 30 minu~es to 135-140C. ~t this point
2 parts of silane were added and reacted with the chlorobutyl for
30 minutes with mixing. Subsequently the epoxy resin was added and
mixed for 15 minutes at 145-150C, and thereafter the remaining 1.5
parts of silane were added and reacted with the epoxy for 30
minutes prior to dumping the composition from the kneader.
The mastic composition was tested using a sandwich techni-
que. Thus two aluminium spacers (wrapped with release paper) were
sandwiched between two glass plates which had been cleaned and
dried with acetone, and the cavity was filled to a contact area of
25 x 50 x 7,5 mm with the mastic delivered from a hot gun having a
body temperature of about 180C. The set was then tested by pulling
at 5 cm/min in shear; the Mooney viscosity was also measured. These
measurements, which were made on the fresh composition and on com-
position which had been aged for one year, are given in Table 2.
Adhesion values marked more interfacial values, to other val.ues
reflect cohesive failure.
Examples 2 and 3, and Comparison Example 4
Example 1 was substantially repeated but using ingredients
such that the overall compositions produced had the formulation
shown in Table 1.
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l Table I
Example1 ___ 2 3_ _ _4
Chlorobutyl 1068 40 30 40 40
Vistanex LM~MS 60 70 30 60
Vistanex MML-140 - - 30
FEF 50 50 50 50
Omya BL 100 100 100 100
Escorez 1304 100 100 100 100
Silane Z-6020 2+1.51.5~1.5 2~1.5 2
lO Epikote 1007 - 10 10 10
Table 2
Example 1 1 2 3 4
_ _ Unaged Aged Unaged Unaged Una
Adhesion (kg)
Temperature
34 41 26 32 ~ 24
65C 3.1
80C - 2.2~ 1.0 2.3~ 1.7
Mooney Viscosity ML (1~14)
20 50C 69 89 ~7 75 63
70C 28 34 19 32 21
90~C 15 18 ~ 18 10
110-C 8 10 5 13 6
_. . . . . .. . . .
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1 As may be concluded from the above resultsf the presence
of the epoxy resin in the formulation improves the adhesion
and has a low effect on cohesion. Moreover the viscosity
and cohesion of the mastic composit:ion decrease as the ratio
of chlorobutyl to polyisobutylene is decreased (a decrease
in hot viscosity being a means of improving the contact
surface and hence adhesion). Furthermore it may be deduced
that increasing the molecular weight of the polyisobutylene
which is admixed with the composition produced according to
1~ the invention leads to an increase in the hot cohesion.
