Note: Descriptions are shown in the official language in which they were submitted.
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WO 97/48778 PCT/EP97/02995
A Reactive Hotmelt Adhesive Composition for Insulating Glass
This invention relates to hotmelt adhesive compositions and to their
use, more particularly for the manufacture of double glazing or multiple
glazing.
Insulating glass is now widely used in the building industry and, to a
5 large extent, in vehicle manufacture by virtue of its many advantages,
including in particular imp~oved thermal and acoustic insulation in relation to
single glazing. It is known that multiple glazing systems consist of two or
more layers of glass arranged parallel to one another and joined at their
edges in such a way that the space between the layers is sealed off from the
10 ambient air so that no moisture is able to penetrate into that space. In
addition, the edge bond/seal is designed to withstand all the various
mechanical and chemical stresses which arise out of varying climatic
condi~iol1s. In many cases, the space in question is even filled with dry gases
which increase thermal insulation and acoustic insulation in relation to air
1 5 fillings.
In co""nercially available multiple glazing units, rigid spacers keep the
layers of glass at the required distance apart from one another. In the most
common embodiment, the spacer consists of an aluminium or steel hollow
section. It is arranged near the edges of the glass layers in such a way that,
20 together with the edges of the glass layer, the spacer forms an outwardly
facing channel for accommodating sealants and adhesives. Normally, that
side of the spacer which faces the space between the layers of glass has
small openings and the hollow interior of the spacer is used to accommodate
a drying agent to adsorb moisture and any solvent residues present in the air
25 or gas space between the layers of glass. This prevents moisture from
condensing on the inside of the glass layers at low ambient temperatures. In
high-quality multiple glazing systems, a sealant with a good barrier effect
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WO 97/48778 2 PCT/EP97/02995
against water vapor is provided between those surfaces of the spacer which
face the glass layers and the glass surface. Formulations based on
polyisobutylene and/or butyl rubber are generally used as the sealant. The
~1annel formed by the outwardly directed face of the spacer and the margins
5 of the glass layers is generally filled with a two-component adhesive/ sealantwhich bonds/seals the multiple glazing unit with sufficient strength. The
adhesive/sealant used must show good adhesion to the glass and, in
addition, must be sufficiently elastic to withstand the expansion and
conl~ion move",enls of the glass layers under varying climatic conditions.
Accordingly, the manufacture of high-quality multiple glazing units of
the type in question naturally involves a number of complex process steps
and is extremely expensive despite a high degree of automation on large
assembly lines. As a result, there has been no shortage of attempts in the
past to simplify the complex process steps involved in the production of
multiple glazing and, in particular, to eliminate the need for pre-profiled
spacers.
The so-called USystem Biver" consists, for example, of a thermoplastic
inner strand of which the polymer component is preferably composed of
polyisobutylene or butyl rubber and which contains a molecular sieve for
adsorbing moisture. This strand faces the space between the glass layers
and is initially extruded onto one layer of glass, after which the second layer
of glass is positioned over the first and the two glass layers are then pressed
together until they are at the required distance apart. Thereafter the outer
margin is sealed by a generally two-component adhesive/sealant. In this
arrangement, the inner strand of the thermoplastic polymer performs the
function of the spacer and carries the drying agent and, in addition, acts as
the main barrier against water vapor. The outer generally two-component
adhesive/sealant provides for the mechanical strength of the double glazing
system. This system is described in numerous patents/applications, cf. for
example DE-C-25 55 381, DE-A-25 55 383, DE-A-25 55 384 and EP-A-176
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WO 97/48778 3 PCT/EP97/02995
388.
DE-A-44 07 892 describes a process for the production of double or
multiple glazing systems in which the two or more layers of glass arranged
parallel to one another are kept at a distance and, at their margins, are
5 surrounded by an extrusion-coated frame which holds the layers of glass
apart from one another. According to the document in question, the material
used for extrusion coating is a thermoset, thermoplastic or ceramic material.
The composition of the injection molding material is not disu ~ssed, nor are
any details provided as to ~vhether and how the gas or the air in the space(s)
10 between the glass layers can be kept dry.
EP-A- 517 067 describes a deformable strip-like extrudate for sealing
and maintaining the distance between two layers of insulating glass. The
deformable strip consists of a flow-resistant polymer matrix which, at its
center, contains a flat wave-shaped material which extends perpendicularly
15 of the layers of glass and which is in i"li"~ale contact with the polymer matrix.
This flat wave-shaped m~le, ial performs the function of the spacer and, at the
same time, acts as a water vapor barrier. The volume of the polymer matrix
which faces the space between the layers of glass preferably contains a
drying agent. A semi-interpenetrating network consisting of a butyl rubber
20 and a lightly crosslinked polyisobutylene is proposed as the polymer matrix.
The prefor",ed deformable sealing strip is produced by co-extrusion of the
polymer matrices and the flat wave-shaped material. This preformed sealing
tape is then placed on one of the layers of glass, the second glass layer is
positioned over the first and the two layers of glass are then pressed
25 together. Since no further curing process takes place after application, the
marginal zone between the sealing strip and the glass layer has a tendency
towards cold flow.
DE-A-38 34 400 describes a double glazing unit which consists of two
layers of glasss joined at their edges by a plastic spacer. The spacer
30 consists of two or more different layers of which the inner layer defines the
, .. . .. .
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WO 97/48778 4 PCT/EP97/02995
interior space and consists of a cured adhesive which conl&ins a moisture-
absorbing sub~lance while the outer layer consisls of a cured adhesive which
is di~ere, lt from the adhesive forming the inner layer. The inner layer of the
adhesive consists of polymers with a relatively high permeability to water
5 vapor and may additionally contain a powder-form drying agent, for example
a molecular sieve, while the outer adhesive layer is said to have a lower
specific permeability to water vapor than the inner layer. Polyurethanes or
silicone rubbers are proposed for the inner layer while a polysulfide-based
adhesive is proposed foF the outer layer. This system has the advantage
10 over the above-mentioned double glazing systems that both layers of
adhesive consist of reactive materials which crosslink after application so thatthe mechanical cohesion of the layers of glass is better, even under
weathering influences. The disadvantage of this process is that two different
materials have to be applied in two process steps.
WO 95/13449 describes sealing profiles preformed for this purpose.
The sealing profiles consist of a completely or partly crosslinked polyiso-
butylene copolymer as the polymer matrix and contain an aluminium foil as
a water vapor diffusion barrier. The disadvantage of this system is that the
spacer system is made up of several different layers which complicates the
20 production process and which is also unfavorable from the point of view of
disposal and/or recycling.
EP-A-232 873 describes sealants for the production of spacer-free
double glazing systems based on 20 to 80% by weight of epoxidized natural
rubber, 5 to 30% by weight of at least one other epoxy compound and an
25 amine or mercaptan containing trialkoxysilyl groups as crosslinking agent andtypical additives, such as coupling agents, tackifiers, plasticizers, fillers,
drying agents, antiagers and UV filters. Although double glazing systems
such as these show excellent resistance to ageing, their main disadvantage
is that they can only be produced as two-component systems where the two
30 reactive components can only be mixed immediately before application.
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WO 97/48778 5 PCTIEP97/02995
It has now been found that multiple glazing systems can be produced
particularly inex~ensively by using hotmelt adhesive compositions which
contain a mixture of at least one reactive binder and at least one non-reactive
binder, at least one reactive binder consisting of silane-functional
5 polyisobutylene and/or silane-functional hydrogenated polybutadiene and/or
silane-fi nc~ional poly-a-olefin and the non-reactive binder(s) being selected
from the group consisting of butyl rubbers, poly-a-olefins, polybutenes,
rubbers based on styrene block copolymers, rubbers based on statistical
diene hol"opolymers and/or copolymers.
The p, efe" ecJ silane-functional groups of the reactive binder(s) can be
represented by formula (1):
R2 R'
¦ 2-b 3-a
-A--Si--O--''i X, (1)
Xb -n
where -A- can represent
-(CH2)m - (2)
-S~(CH2)m ~
-N-C-N R3
11
H O H
and R' and R2 may be the same or different and represent an alkyl group
containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon
35 atoms or an arylalkyl group containing 7 to 20 carbon atoms, X can be a
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WO 97/48778 6 PCT/EP97/02995
hydroxyl group or a hydrolyzable group, a can be an integer between 0 and '
3 and b can have a value of 0, 1 or 2, the sum of a and b being 1 or greater
than 1, and n is a number of 0 to 18, m is an integer of 0 to 4 and R3
represents
- (CH2)m or
- (CH2)m -N- (CH2)m -
;
The reactive binder(s) contain(s) at least one silane-functional group
co"esponding to formula (1). In a preferred embodiment, they contain on a
statistical average between 1 and 3 silane-functional groups per molecuie.
The silane-functional groups are situated either at the ends of the macro-
15 "~c'e~ ~'e (telechelic polymers) or are sl;llislic~lly distributed over the polymerchain. The hydrolyzable group X may be any hydrolyzable group known per
se, for example an alkoxy group, acetoxy group, amino group, oxime group
or amide group. The hydrolyzable group is preferably an alkoxy group, more
preferably a methoxy or ethoxy group.
The silane-functional polyisobutylenes, silane-functional polybuta-
dienes or silane-functional poly-a-olefins are produced in known manner. A
telechelic polymer containing olefinically unsaturated terminal groups is
normally formed in the first stage and is reacted with organosilicon com-
pounds in a second stage to form silane-functional polyisobutylene,
hydrogenated polybutadiene or poly-a-olefin. The various versions of this
production process for silane-functional polyisobutylenes or polybutadienes
are described, for example, in the following patent applications: EP-A-287
025, EP-A- 452 875, EP-A- 434 840, EP-A-252 372, EP-A-79 456, EP-A- 537
660.
Other possible methods for the production of silane-functional
polyisobutylenes or hydrogenated polybutadienes are described in EP-A-312
.... , .. ~ ~ .. ..
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WO 97/48778 7 PCTIEP97/02995
967. In addition, a hydroxyfunctional polyisobutylene, hydroxyfunctional
polybutadiene or hydroxyfunctional poly-a-olefin can be prepared in a first
process step and reacted with an isocyanate-functional silane in a second
step.
Another possible method for producing the silane-functional binders
comprises reacting the nonfunctional polyisobutylenes, hydrogenated
polybutadienes or poly-a-olefins with corresponding organofunctional silanes
in known manner in a grafting reaction. The silane groups are of course
st~tistic~lly distributed in the polymer chain.
In principle, any rubber-like polymer with no functional groups may be
used for the non-reactive binder. However, since the composition as a whole
is pr~rer~bly intended for the production of spacer-free double glazing edge
seals/bonds, the non-reactive binder should also be selected from polymers
which guarantee low permeability to gases and, in particular, low permeability
to water vapor of the glazing unit as a whole. The non-reactive binders may
be selected from the group consisting of poly-a-olefins, rubbers based on
styrene block copolymers, rubbers based on statistical diene homopolymers
and/or copolymers and, in particular, polybutenes or butyl rubbers.
Suitable poly-a-olefins are, for example, ethylene/propylene elasto-
mers, such as ethylene/propylene copolymers and terpolymers of ethylene
and propylene with an unconjugated diene (EPDM). Propene/butene
copolymers and ethylene/vinyl acetate are also suitable.
The rubbers based on styrene block copolymers are the diblock and
triblock copolymers of styrene with a diene, for example butadiene or
isoprene, which are commercially available, for example, under the name of
Kraton from Shell. Hydrogenated or partly hydrogenated block copolymers
may also be used.
Examples of the statistical diene homopolymers and copolymers are
polybutadiene, polyisoprene, copolymers thereof and styrene/butadiene
copolymers, acrylonitrile/butadiene copolymers and the partly hydrogenated
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WO 97148778 8 PCT/EP97/02995
or completely hydrogenated diene polymers of the last-mentioned group.
Natural rubber, more particularly epoxidized natural rubber, may also
be used as a non-reactive binder.
By virtue of their particularly favorable barrier effect against water
5 vapor and gases, polybutenes and/or polyisobutene, polyolefins produced by
slereospe~fic polymerization of 1-butene or isobutene and butyl rubbers, i.e.
copolymers or isobutylene with isoprene, are most particularly preferred.
The hotmelt adhesive compositions according to the invention may
also contain plasticizers, although the plasticizers should be chosen with
10 particular care according to the following criteria:
- An extremely low percentage content of volatile components in order
to avoid so-called fogging over the life of the double glazing unit.
Fogging is a well-known phenomenon whereby small quantities of
volatile cor"ponents of the binder system first enter the space between
the layers of glass and condense on the colder parts thereof.
- The barrier effect of the polymer matrix against water vapor and gases
should not be adversely affected by the plasticizer.
Examples of suitable plasticizers are the phthalate plasticizers known
per se based on phthalic acid alkyl or aryl esters, providing their volatile
components are so small in number that the plasticizers do not cause any
fogging and, in addition, the phthalate plasticizers are compatible with the
binder system, i.e. have no tendency towards exudation.
Liquid polybutenes and polyisobutenes are most particularly preferred
plasticizers.
The hotmelt adhesive compositions according to the invention may
additionally contain components known per se, including in particular water-
binding fillers, preferably the zeolites of the 3 A type known as molecular
sieves in powder form. In addition, fine-particle inert fillers, for example
ground or precipitated chalks, kaolins, clays and carbon blacks may be used.
The chalks, kaolins or clays may be used both in their surface-hydrophobi-
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WO 97/48778 9 PCT/EP97/02995
cized form or even without any surface pretreatment.
In addition, the compositions contain organofunctional silanes as
coupling agents and/or crosslinking agents, including for example 3-
glycidyloxypropyl trialkoxysilane, 3-acryloxypropyl trialkoxysilane, 3-amino-
propyl trialkoxysilane, vinyl trialkoxysilane, N-aminoethyl-3-aminopropyl
methyl dialkoxysilane, phenylaminopropyl trialkoxysilane, aminoalkyl
trialkoxydisilane or i-butyl methoxysilane. A particularly preferred alkoxy
group is the methoxy or ethoxy group.
Suitable catalysts iare any known compounds which are capable of
catalyzing the hydrolysis of the hydrolyzable groups of the silane groups and
the subsequent condensation of the Si-OH group to siloxane groups
(crossli"king reaction or coupling function). Organic compounds of divalent
and tetravalent tin are most particularly preferred.
The choice of the antiager used, if any, is govemed by the composition
of the binder. Antioxidanls of the sterically hindered phenol, thioether or highmo'ec~ weight mercapto compound type and UV stabilizers of the known
ber~o~ 'P, benzophenone or HALS (hindered amine light stabilizer) type
may be used. It can be of advantage to add known anti-ozonants. In
exceptional cases, hydrolysis stabilizers may also have to be added.
Where the hotmelt adhesive compositions according to the invention
are used for the production of multiple glazing units, the multiple glazing unitthus produced is distinguished by the following features in relation to the prior
art:
- the adhesive mixture acts both as a spacer and as a matrix for the
moisture-absorbing substance,
- it also forms an elastic bond/seal at the edges of the glass layers,
- the water harmful to the useful life of the double glazing unit is not only
bound in the matrix by the molecular sieve, it is also at least partly
consumed by a chemical reaction in the curing process.
A particular advantage is that all the process steps hitherto involved
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WO 97/48778 10 PCT/EP97/02995
in the formation of a conventional edge seal/bond are now combined into a
single step. Another advantage is that, because it consists of only one
material, a system of the type in question can be recycled after dismantling
of the double glazing unit at the end of its useful life because, in conl, asl to
5 the prior art, it is not a composite material of polymer matrices differing in their composition.
The compositions according to the invention preferably consist of
(a) silane-functional polyisobutylene,
silane-functional hydrogenated polybutadiene
or silane-functional poly-a-olefin 20 -70% by weight
(b) butyl rubber 5 -30% by weight
(c) poly-a-olefin 5 -30% by weight
(d) molecular sieve of the zeolite 3A type20 -30% by weight
(e) carbon black 5 -30% by weight
(f) catalyst 0.1- 2%byweight
(g) organosilane 0.1- 2%byweight
The compositions may be produced in known manner by high-shear
mixing of the components to homogeneity, optionally in vacuo or in an inert
gas atmosphere. The components being mixed may have to be heated or
20 cooled. Since the hotmelt adhesive compositions react with moisture by
crosslinking, the compositions have to be protected against moisture pending
their final application by the user in order to guarantee adequate stability in
storage.
In the embodiment as a one-component adhesive/sealant, all the
25 above-mentioned components are mixed together in the production process.
In the two-component embodiment, the catalyst(s) (f) are separately prepared
in a paste of the non-reactive binder (b) and/or (c) and part of the filler (e) and
optionally plasticizer as component B. The other constituents are prepared
as component A, both components being mixed immediately before
30 application. In another embodiment, component A consists of constituents
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WO 97/48778 11 PCT/EP97/02995
(a) to (g) while component B consists of a water-containing paste, the water
optionally being present in this paste in the form of water-releasing com-
pounds, for example salts containing water of crystallization. One advantage
of this procedure is that it enables the compositions to be formulated in such
5 a way that a particularly rapid crosslinking reaction takes place, so that a
double glazing seal/bond thus formed is capable of withstanding severe
mechanical stressing after a particularly short time.
To produce the double glazing units, the layers of glass to be joined
are either kept at the precl~tel ",ined distance apart in known manner and the
10 c~"~posilions are injected into the space between the layers at their marginsby means of an extruder-like applicator, optionally with heating and profiling.
By virtue of the hotmelt-like consistency of the composition, the edge
seal/bond develops an early strength after cooling of the adhesive composi-
tion sufficient to enable the double glazing units to be immediately further
15 p~ucesserl~ transported or stored. Ultimate strength is developed through the~osslinking of the silane groups of the reactive binder in combination with the
organosilane added by reaction with the moisture in the space between the
glass layers and/or the ambient air.
In another embodiment, the hotmelt adhesive is applied to the
20 peripheral edge of one layer of glass, optionally with heating and profiling, the
second layer of glass or additional layers of glass are then positioned over
the first in such a way that the layers of glass are exactly aligned one above
the other. They are then pressed together in such a way that the adhesive
completely wets the edges of both or all the layers of glass and the predeter-
25 mined inter-layer spacing is reached. In this embodiment, too, the early
strength of the edge seal/bond is developed during the cooling process
whereas ultimate strength is achieved by crosslinking with moisture.
As mentioned above, the two components of the two-component
hotmelt adhesives are mixed immediately before the application steps just
30 described. The edge seal/bond develops its ultimate strength more quickly
in this embodiment than in the one-component version.
