U.S. patent application number 10/476525 was filed with the patent office on 2004-07-01 for adhesive filled with surface-treated chalk and soot.
Invention is credited to Kuelling, Annemarie, Pfenninger, Ueli, Stadelmann, Ursula.
Application Number | 20040127622 10/476525 |
Document ID | / |
Family ID | 8177359 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040127622 |
Kind Code |
A1 |
Pfenninger, Ueli ; et
al. |
July 1, 2004 |
Adhesive filled with surface-treated chalk and soot
Abstract
The invention relates to an adhesive composition containing a
special silane cross-linking polymer and fine-particle coated
calcium carbonate and soot. 20 to 50 ml of fine-particle coated
calcium carbonate and soot are provided for every 100 g of polymer,
and the volume ratio of fine-particle coated calcium carbonate and
soot is between 70:30 and 30:70. The inventive adhesive composition
is characterized by having good mechanical properties, a high
electrical volume resistance and a good applicability.
Inventors: |
Pfenninger, Ueli; (Au,
CH) ; Stadelmann, Ursula; (Zurich, CH) ;
Kuelling, Annemarie; (Winterhur, CH) |
Correspondence
Address: |
Oliff & Berridge
PO Box 19928
Alexandria
VA
22320
US
|
Family ID: |
8177359 |
Appl. No.: |
10/476525 |
Filed: |
November 3, 2003 |
PCT Filed: |
April 18, 2002 |
PCT NO: |
PCT/IB02/01247 |
Current U.S.
Class: |
524/425 |
Current CPC
Class: |
C08G 18/10 20130101;
C08K 3/26 20130101; C08G 2190/00 20130101; C09J 175/04 20130101;
C08G 18/289 20130101; C08K 3/04 20130101; C08G 18/10 20130101 |
Class at
Publication: |
524/425 |
International
Class: |
C08K 003/26 |
Foreign Application Data
Date |
Code |
Application Number |
May 10, 2001 |
EP |
01111158.0 |
Claims
1. An adhesive composition comprising at least one
silane-crosslinking polymer, fine-particle coated calcium
carbonate, and soot, characterized in that a) the at least one
silane-crosslinking polyurethane polymer is constructed in
accordance with the following formula (I): 13where R.sup.1 stands
for an alkyl group having 2 to 8 carbon atoms, linear or branched,
R.sup.2 stands for an alkyl radical having 1 to 8 carbon atoms,
R.sup.3 stands for an alkyl radical having 1 to 5 carbon atoms, a
stands for 0 or 1, Z stands for a sulfur or an NR.sup.4, where
R.sup.4 stands for a hydrogen atom or an organic radical, for
example, an alkyl group or an aryl group having 1 to 20 carbon
atoms, or a compound having ester groups such as, for example, a
moiety of the formula (II) 14where R.sup.5 stands for an alkyl
group having 1 to 8 carbon atoms, n denotes a number from 2 to 4,
and A stands for a radical of a polyurethane prepolymer with the
functionality n, b) the fine-particle coated calcium carbonate, is
a calcium carbonate coated with fatty acid, especially stearate,
and having a particle size of from 0.05 to 1 micron and a density
of approximately 2.6-2.7 g/ml, and c) the soot is soot with a
density of approximately 1.8 g/ml, in particular soot having a
large surface area, there being from 20 to 50 ml of fillers b)+c)
per 100 g polymer a), and the volume ratio of b) to c) being
between 70/30 and 30/70.
2. The adhesive composition according to claim 1, characterized in
that A stands for a polyurethane radical obtainable by reacting
commercially customary polyols with an excess of commercially
customary polyisocyanates, the average molecular weight of A
usually being in the range from 500 to 100 000 g/mol, and A
containing at least n urethane groups.
3. The adhesive composition according to claim 1 or 2,
characterized in that A denotes a radical of the formula (III)
15where Q stands for an aromatic, aliphatic or cycloaliphatic
radical which represents in particular a polyisocyanate, with
special preference a commercially customary diisocyanate, following
elimination of two or more isocyanate groups, and P stands for a
radical which represents a polyoxyalkylene-polyol or
polyalkyldiene-polyol, in particular a commercially customary
polyol, following elimination of at least two OH groups, X denotes
a radical of the formula (IV) 16where m independently of one
another denotes 0 to 5 and where Q has the abovementioned
definition and where P.sub.1=P or denotes P(X).sub.u, with the
proviso that not more than one P.sub.1 is P(X).sub.u and where u=1
or 2, and where the average molecular weight of A is preferably in
the range from 500 to 100 000 g/mol, 4. The adhesive according to
one of claims 1 to 3, characterized in that the radical A has a
funtionality n=2 and can be depicted by formula (V) 17where Q
stands for a radical which represents an aliphatic, cycloaliphatic
or aromatic polyisocyanate following elimination of at least 2
isocyanate groups, in particular a dissocyanate, following
elimination of both isocyanate groups, and P stands for a radical
which represents a polyalkyldiene- or polyoxyalkylene-polyol
following elimination of at least 2 of OH groups, in particular a
diol, following elimination of both OH groups, and m=0 to 5.
5. The adhesive according to one of the preceding claims,
characterized in that Q is the radical which remains following
elimination of 2 isocyanate groups from one of the isocyanates from
the following group: 2,4- and 2,6-toluene diisocyanate, 4,4'- and
2,4'-diphenylmethane diisocyanate, isophorone diisocyanate, 2,2,4-
and 2,4,4-trimethyl-1,6-hexamethylene diisocyanate,
1,6-hexamethylene diisocyanate, m- and p-tetramethylxylylene
diisocyanate, the isomers of 4,4'- or 2,4'-dicyclohexylmethane
diisocyanate, polymers or oligomers of these isocyanates, and
mixtures of two or more of the stated isocyanates.
6. The adhesive according to one of the preceding claims,
characterized in that P is the radical that remains following the
elimination of at least two OH groups from a polyol from the
following group: polyetherpolyols, which are the polymerization
product of ethylene oxide, propylene oxide or butylene oxide or
mixtures thereof, or hydroxy-terminated polybutadiene polymers,
especially polyols having an OH functionality of from 1.8 to 3 and
a molecular weight from 500 to 20 000 g/mol.
7. The adhesive according to one of the preceding claims,
characterized in that it further comprises one or more of the
following constituents: plasticizers, especially organic esters and
polybutenes, solvents, further organic or inorganic fillers, such
as other calcium carbonates, kaolines, aluminas, silicas, fibers,
pigments, thickeners, heat stabilizers or UV stabilizers, adhesion
promoters, dryers, catalysts.
8. A process for preparing an adhesive .alpha.-cording to one of
the preceding claims, characterized in that the at least one
silane-terminated polyurethane prepolymer is prepared by
reacting--in a first step--polyols with an excess of polyisocyanate
to give a prepolymer having isocyanate end groups and in that these
isocyanate end groups are subsequently reacted with at least one
organofunctional silane containing an isocyanate-reactive group,
whereupon the prepolymer thus obtained is subsequently mixed in the
absence of moisture with soot dried beforehand and with
fine-particle coated calcium carbonate dried beforehand.
9. The process according to claim 8, characterized in that the
organofunctional silane is a compound with the formula (VI) 18where
R.sup.1, R.sup.2, R.sup.3 and a have a definition described above
and Y stands for --SH or --NH.sub.2 or --NHR.sup.4, and R.sup.4
likewise has the definition described above, especially aminosilane
containing as R.sup.4 the following moiety 19where R.sup.5 stands
for an alkyl group having 1 to 8 carbon atoms.
10. The process according to claim 8 or 9, characterized in that
the polyol- and the isocyanate are reacted at temperatures of from
50 to 100.degree. C., using where appropriate suitable catalysts as
well, the isocyanate component being employed in excess, and where
this polyurethane prepolymer having isocyanate end groups is
subsequently reacted with the organofunctional silanes
stoichiometrically or in a slight excess.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of European patent
application no. 01 111 158.0, which was filed May 10, 2001 and
whose entire disclosure content is hereby incorporated by
reference.
TECHNICAL FIELD
[0002] The present invention relates to filled adhesives,
especially filled silane-crosslinking adhesives.
[0003] Prior art
[0004] Polyurethane polymers have long been known as especially
suitable materials for adhesive applications requiring high
flexibility in conjunction with good strengths. One-component
systems, in which isocyanate end groups of the polyurethane polymer
react with atmospheric moisture to crosslink the polymer, have the
advantage of simple applicability, since they require no metering
of the second component and no mixing operation. Systems of this
kind find widespread application as adhesives and sealants in
industry and in construction. A further development of these
polyurethane polymers involves replacing the isocyanate functional
groups by silane groups, which likewise crosslink with atmospheric
moisture to form Si--O--Si bonds. The preparation of
silane-crosslinking polyurethane polymers by reaction of the
terminal isocyanate groups with mercapto-functional or
amino-functional silanes is described for example in U.S. Pat. No.
3,632,557 (Union Carbide) and U.S. Pat. No. 5,364,955 (Bayer). U.S.
Pat. No. 3,632,557 (Union Carbide) describes the preparation of
silane-crosslinking organic polymers by reacting terminal
isocyanate groups of polyurethane prepolymers with
mercapto-functional or amino-functional silanes. These polymers may
comprise, inter alia, a filler. Neither calcium carbonate nor soot
are listed as examples.
[0005] On the basis of said patent it is indeed possible to prepare
silane-crosslinking polyurethane adhesives and sealants, but the
mechanical values thereby achievable for formulations having raw
materials costs that are in tune with the market range within the
order of magnitude of 1.5 MPa tensile strength and 150% elongation
at break, which is inadequate for use as an adhesive in the
automobile industry.
[0006] U.S. Pat. No. 5,364,955 (Bayer) describes, for the
preparation of silane-crosslinking polyurethane polymers, special
secondary aminosilanes (aspartic ester derivatives) which are
attached to polyurethane prepolymers having isocyanate end groups.
The silane-terminal polymers can be used for formulating sealing
materials. Indications of especially suitable fillers for achieving
special properties are not mentioned.
[0007] The advantage of crosslinking via silane groups is that, on
the one hand, crosslinking is not accompanied by the formation of
any CO.sub.2, which under certain circumstances can lead to
disruptive bubbles in the adhesive, and that, on the other hand,
the user does not come into contact with monomeric isocyanates,
which are a potential health hazard.
[0008] In addition to these documents which are unspecific as
regards the fillers there are already works which deal with the
attaining of special properties through the use of specific
fillers.
[0009] U.S. Pat. No. 6,001,946 (Witco) describes more or less the
same silane-terminal polyurethane prepolymers, based on aspartic
ester derivatives of amino-functional silanes, as U.S. Pat. No.
5,364,955. Reinforcing fillers listed include fumed silica,
precipitated silica, and calcium carbonate, with treated calcium
carbonate having a particle size of from 0.07 to 4 microns particle
size being referred to as a preferred filler. These fillers can be
used alone or as a filler combination. As a preferred quantity of
filler mention is made of from 80 to 150 parts per 100 parts of
polymer. On the basis of that patent it is possible to achieve
adhesives having tensile strengths of approximately 1.5 MPa with
approximately 300% elongation. Adhesives of this kind are not
strong enough for use in the automobile industry.
[0010] EP 0 676 403 (Witco) describes silane-terminal polyurethane
polymers containing arylamino-functional silanes. Sealants based on
these polymers are said to have higher elongation, higher
flexibility, and a lower elasticity modulus than the prior art at
that time. Described as preferred calcium carbonate fillers are
treated types having particle sizes of from 0.05 to 10 microns in
an amount of up to 100 parts per 100 parts of polymer. On the basis
of that patent it is possible to achieve adhesives having tensile
strengths of approximately 2.8 MPa at 300% elongation. This tensile
strength is still too low for application in the automobile
industry. Additionally it has been found that silane-crosslinking
polyurethane polymers which comprise phenyl-amino silane have a
poor aging stability in the cured state under hot storage.
[0011] U.S. Pat. No. 5,703,146 (Kaneka) describes sealants composed
of 100 parts of silane-terminal oxypropylene polymer with a narrow
molecular weight distribution, from 100 to 200 parts of calcium
carbonate with a particle size of not more than 0.5 micron, and
surface-treated with a fatty acid, and a number of further
additions. The polymer has a fraction of 15-35% in the overall
composition. Through the combination of the polymer having the
narrow molecular weight distribution and hence low viscosity with
the fine-particle coated calcium carbonate stability is obtained
adequately in combination with effective extrudibility, but
sufficiently high tensile strengths are not obtained.
[0012] U.S. Pat. No. 4,222,925 (Inmont Corporation) describes an
adhesive with a rapid curing rate and high strength, which is used
in combination with a primer in automobile engineering to glue in
windshields. The adhesive is composed of a silane-terminal
polyurethane polymer (prepared as described in U.S. Pat. No.
3,632,557), a special amino-functional silane, and soot with a
water content of not more than 0.05%. The addition of dried soot is
said significantly to increase the mechanical strength of the
adhesive. General indications of the amount of soot used are
absent, though example 2 discloses the use of 35 parts of soot per
100 parts of polymer, which leads to very high mechanical values.
An adhesive formulation with a total fraction of 73% polymer in the
formulation is too expensive, however, for a utility in tune with
practice.
[0013] WO 99/55755 (Essex) describes a method of gluing windows
into a structure. The adhesive used is based on a silane-terminal
oxyalkylene polymer, a silane-terminal polyurethane polymer, or
similar silane-terminal systems. The polymer preferably has a
fraction in the overall composition of the adhesive of from 45 to
85%, contains a tin catalyst in a preferred amount of from 0.1 to
0.4%, a special amino-functional silane and other additives. Soot,
calcium carbonate, and other reinforcing fillers are listed as
possible additives, with preference being given to soot as the sole
reinforcing filler used. An amount of reinforcing filler of from 20
to 33%, based on the overall adhesive composition, is preferred,
and compositions having tensile strengths of up to 1028 psi (=7.1
MPa) are disclosed. As a consequence of the high soot fraction in
the adhesive it is impossible to achieve, with these adhesives, the
high electrical volume resistance required for adhesive bonds in
the automobile industry.
[0014] It is also already known to use both fine-particle coated
calcium carbonate and soot as an addition to silane-crosslinking
polymers.
[0015] EP 0 819 749 (Simson) describes silane-crosslinking
adhesives and sealants with high electrical resistance which are
suitable for industrial applications, such as the gluing in of auto
windshields, or, in particular, as an adhesive and sealant for
electrical appliances. These adhesives and sealants must include
the following components: silane-terminal polymer, crosslinking
catalyst, dryer, adhesion promoter, and rheology controller, it
being possible for from 25% to 55% of the composition to be in the
form of a calcium carbonate filler. When precipitated calcium
carbonate grades coated with fatty acid are used, the viscosity of
the composition is said to be increased, and the stability
and--given the choice of a mixture of precipitated and
unprecipitated calcium carbonate--the mechanical strength are said
to be improved. Soot, in an amount of from 0.2 to 5% based on the
overall composition, is mentioned as a pigment.
[0016] EP 0 931 800 (Witco Corp.) describes sealants having
improved mechanical values, good curing rate, low surface tack and
not excessively high viscosity. They are based on a silane-terminal
polyurethane prepolymer which is prepared by reacting an
OH-terminal polyurethane prepolymer with an isocyanate-functional
silane. Possible reinforcing fillers mentioned include fumed
silica, precipitated silica, and calcium carbonate, with soot being
proposed as the principal filler in order to bring about even
further reinforcement. Treated calcium carbonates having particle
sizes of from 0.07 to 4 microns are preferred fillers. The fillers
can be used alone or in combination, with the stated preferred
amount of filler being from 80 to 150 parts per 100 parts of
polymer. The maximum tensile strength achieved in the examples is
2.7 MPa.
[0017] None of these documents reveals any indication as to what
must be the construction of an adhesive composition based on a
silane-terminated polymer in order to meet the requirements imposed
in the automobile industry. None of these documents suggests that,
using a special type of silane-terminated polymers, namely special
silane-crosslinking polyurethane prepolymers, there exists a range
within which the silane-crosslinking polyurethane prepolymers can
be filled with a combination of fine-particle coated calcium
carbonate and soot in such a way as to provide the properties
necessary for the preparation of adhesives for the automobile
industry. Owing to the high mechanical loads of the adhesive layer,
these properties are a high strength of the adhesive in combination
with good flexibility and, in order to achieve corrosion-resistant
adhesive bonding between different metals, a high electrical volume
resistance of the cured adhesive. More specifically these
properties are
[0018] a tensile strength of at least 4.5 MPa,
[0019] an elongation at break of at least 250%,
[0020] an electrical volume resistance of at least 10.sup.8 ohm cm,
and
[0021] good applicability, all in combination with
[0022] raw materials costs that are not too high.
[0023] A high electrical volume resistance is also important
because an excessive conductivity of the adhesive layer can cause
disruptions to the receiving of radio when rear screens with
built-in aerials are glued in.
[0024] A further prerequisite for an adhesive in tune with practice
is its good applicability. In other words, the uncured adhesive
must be able to be extruded from the cartridge with reasonable
force in the case of repair. The extrusion force from the cartridge
through an opening with a diameter of 5 mm ought not to exceed a
level of 2 000 N.
[0025] Moreover, the raw materials costs of a silane-crosslinking
polyurethane adhesive in tune with practice must not exceed a
certain limit. Formulations which have a high polymer fraction of
70% or more are therefore not in tune with the market.
[0026] Meeting all of these requirements is not possible with a
silane-crosslinking adhesive in accordance with the present state
of the art.
[0027] Surprisingly it has been found that silane-crosslinking
polyurethane adhesives that meet the aforementioned requirements
for the adhesive bonding of components in the automobile industry
can be formulated by combining a special, silane-crosslinking
polyurethane polymer in a defined range with fine-particle coated
calcium carbonate and soot.
Depiction of the Invention
[0028] The present invention accordingly provides adhesives able to
meet the requirements specified above.
[0029] Such adhesives of the invention comprise the following three
constituents:
[0030] a) silane-crosslinking polyurethane polymer constructed in
accordance with the following formula (I): 1
[0031] where R.sup.1 stands for an alkyl group having 2 to 8 carbon
atoms, linear or branched,
[0032] R.sup.2 stands for an alkyl radical having 1 to 8 carbon
atoms,
[0033] R.sup.3 stands for an alkyl radical having 1 to 5 carbon
atoms,
[0034] a stands for 0 or 1,
[0035] Z stands for a sulfur or an NR.sup.4, where R.sup.4 stands
for a hydrogen atom or an organic radical, for example, an alkyl
group or an aryl group having 1 to 20 carbon atoms, or a compound
having ester groups such as, for example, a moiety of the formula
(II) 2
[0036] where R.sup.5 stands for an alkyl group having 1 to 8 carbon
atoms,
[0037] n denotes a number from 2 to 4,
[0038] and A stands for a radical of a polyurethane prepolymer with
the functionality n,
[0039] b) fin e-particle coated calcium carbonate, by which is
meant fatty acid-treated calcium carbonates having a particle size
of from 0.05 to 1 micron, with a density of approximately 2.6-2.7
g/ml, and
[0040] c) soot, preference being given to grades having a large
surface area, with a density of approximately 1.8 g/ml,
[0041] there being from 20 to 50 ml of fillers b)+c) per 100 g
polymer a), and the volume ratio of b) to c) being between 70/30
and 30/70.
[0042] Preferably A stands for a polyurethane radical obtainable by
reacting commercially customary polyols with an excess of
commercially customary polyisocyanates, the average molecular
weight of A usually being in the range from 500 to 100 000 g/mol,
and A containing at least n urethane groups. In particular A
denotes a radical of the formula (III) 3
[0043] where Q stands for an aromatic, aliphatic or cycloaliphatic
radical which represents in particular a polyisocyanate, with
special preference a commercially customary diisocyanate, following
elimination of two or more isocyanate groups, and
[0044] P stands for a radical which represents a
polyoxyalkylene-polyol or polyalkyldiene-polyol, in particular a
commercially customary polyol, following elimination of at least
two OH groups,
[0045] X denotes a radical of the formula (IV) 4
[0046] where m independently of one another denotes 0 to 5 and
where
[0047] Q has the abovementioned definition and where
[0048] P.sub.1=P or denotes P(X).sub.u, with the proviso that not
more than one Pi is P(X).sub.u and where u=1 or 2.
[0049] Where the abovementioned conditions are observed the
resultant adhesives are suitable for the sealing adhesive bonding
of components which consist at least in part of metal, as in the
automobile industry, for example. The adhesives have good
mechanical properties, a high electrical volume resistance, good
applicability and reasonable raw materials costs. They can be
applied effectively (i.e., they have an extrusion force of not more
than 2 000 N), they have a tensile strength of at least 4.5 MPa, an
elongation break of at least 250%, and they have an electrical
volume resistance of at least 10.sup.8 ohm cm.
Way(s) of Performing the Invention
[0050] An essential constituent of the adhesive compositions of the
invention is the silane-crosslinking polyurethane polymer which is
constructed in accordance with the following formula (I): 5
[0051] where R.sup.1 stands for an alkyl group having 2 to 8 carbon
atoms, linear or branched,
[0052] R.sup.2 stands for an alkyl radical having 1 to 8 carbon
atoms,
[0053] R.sup.3 stands for an alkyl radical having 1 to 5 carbon
atoms,
[0054] a stands for 0 or 1,
[0055] Z stands for a sulfur or an NR.sup.4, where R.sup.4 stands
for a hydrogen atom or an organic radical, for example, an alkyl
group or an aryl group having 1 to 20 carbon atoms, or a compound
having ester groups such as, for example, a moiety of the formula
(II) 6
[0056] where R.sup.5 stands for an alkyl group having 1 to 8 carbon
atoms,
[0057] n denotes a number from 2 to 4,
[0058] and A stands for a radical of a polyurethane prepolymer with
the functionality n.
[0059] Preferably A stands for a polyurethane radical obtainable by
reacting commercially customary polyols with an excess of
commercially customary polyisocyanates, the average molecular
weight of A usually being in the range from 500 to 100 000 g/mol,
and A containing at least n urethane groups. In particular A
denotes a radical of the formula (III) 7
[0060] where Q stands for an aromatic, aliphatic or cycloaliphatic
radical which represents in particular a polyisocyanate, with
special preference a commercially customary diisocyanate, following
elimination of two or more isocyanate groups, and
[0061] P stands for a radical which represents a
polyoxyalkylene-polyol or polyalkyldiene-polyol, in particular a
commercially customary polyol, following elimination of at least
two OH groups,
[0062] X denotes a radical of the formula (IV) 8
[0063] where m independently of one another denotes 0 to 5 and
where
[0064] Q has the abovementioned definition and where
[0065] P.sub.1=P or denotes P(X).sub.u, with the proviso that not
more than one P.sub.1 is P(X).sub.u and where
[0066] u=1 or 2.
[0067] In the preferred case of n=2 the radical A can be depicted
by the formula (V): 9
[0068] where Q stands for a radical which represents a
diisocyanate, in particular a commercially customary diisocyanate,
following elimination of the two isocyanate groups and P stands for
a radical which represents a polyol, in particular a commercially
customary polyol, following elimination of the two OH groups, and
m=0 to 5.
[0069] Preferred polyisocyanates are diisocyanates. Examples that
may be mentioned include the following isocyanates, which are very
well known in polyurethane chemistry:
[0070] 2,4- and 2,6-toluene diisocyanate, 4,4'- and
2,4'-diphenylmethane diisocyanate, isophorone diisocyanate, 2,2,4-
and 2,4,4-trimethyl-1,6-hex- amethylene diisocyanate,
1,6-hexamethylene diisocyanate, m- and p-tetramethylxylylene
diisocyanate, the isomers of 4,4'- or 2,4'-dicyclohexylmethane
diisocyanate, polymers or oligomers of these isocyanates, and
mixtures of two or more of the stated isocyanates.
[0071] Polyols which, following elimination of at least two OH
groups, produce the radical P are preferably the following raw
materials, which are very well known in polyurethane chemistry, or
mixtures thereof:
[0072] polyetherpolyols, which are the polymerization product of
ethylene oxide, propylene oxide or butylene oxide or mixtures
thereof, or hydroxy-terminated polybutadiene polymers. The polyols
generally have an OH functionality of from 1.8 to 3 and a molecular
weight from 500 to 20 000 g/mol. In addition to said polyols it is
possible in the preparation to use compounds having two or more OH
groups, as well, as chain extenders or crosslinkers, so that their
radicals may likewise contribute to P. Examples that may be
mentioned include 1,4-butane diol and trimethylol propane.
[0073] The silane-terminated prepolymers used in accordance with
the invention can be prepared by reacting, in a first step, polyols
with an excess of polyisocyanate, to give a prepolymer having
isocyanate end groups. These isocyanate end groups are subsequently
reacted with an organofunctional silane containing an
isocyanate-reactive group.
[0074] Suitable organofunctional silanes are compounds with the
formula (VI) 10
[0075] where R.sup.1, R.sup.2, R.sup.3 and a have the definition
described above and Y stands for --SH or --NH.sub.2 or --NHR.sup.4,
and R.sup.4 likewise has the definition described above.
Particularly suitable is an amino silane containing as R.sup.4 the
following moiety (II) 11
[0076] where R.sup.5 stands for an alkyl group having 1 to 8 carbon
atoms.
[0077] Organofunctional silanes of this kind can be prepared from
the corresponding maleic or furmaric diester and an amino silane
where Y=--NH.sub.2 by means of an addition reaction across the
double bond. An example that may be mentioned of an
organofunctional silane compound of this kind is the one below,
prepared from diethyl maleic and
.gamma.-aminopropyltrimethoxysilane: 12
[0078] As polyols it is possible to use the raw materials already
mentioned above as "suppliers" of the radical P, which are very
well known in polyurethane chemistry, or mixtures of such
materials.
[0079] Suitable polyisocyanates for preparing such a prepolymer
include the aliphatic, cycloaliphatic or aromatic isocyanates
having at least two isocyanate groups per molecule, likewise
mentioned already above as "suppliers" of the radical Q.
[0080] The preparation can take place by reacting the polyol
component and the isocyanate component by customary methods, e.g.,
at temperatures of from 50 to 100.degree. C., where appropriate
using suitable catalysts, and employing the isocyanate component in
excess. The reaction product formed is the aforementioned
polyurethane prepolymer having isocyanate end groups. This
prepolymer is subsequently reacted with the isocyanate-reactive
organofunctional silane described, and the aforementioned
silane-terminal polyurethane prepolymer is formed. The
organofunctional silane is used stochiometrically or in a slight
excess in relation to the isocyanate groups.
[0081] Particularly suitable as the fine-particle coated calcium
carbonate described under b) are calcium carbonates which have been
surface-coated with fatty acids, such as stearates, for example,
and which have an average particle size of from 0.05 to 1 micron.
The amount of organic substance ranges between 0.9 and 5% weight
fractions. Examples of grades which are especially suitable are
Winnofil SP and Winnofil SPT from ICI or Socal U1S2 from Solvay.
The density of these materials is from about 2.6 to 2.7 g/ml.
[0082] The soot specified under c) is preferably a grade having a
large surface area and having a density of approximately 1.8
g/ml,
[0083] All possible soot grades are suitable, provided they have
been dried before being mixed into the prepolymer. In order to
reduce the electrical conductivity it is possible to use fully or
partly oxidized soot grades, these grades being more expensive and
therefore being usable only in restricted form--in order to give a
market-compatible product which is not too expensive.
[0084] So that even when using unoxidized soot it is possible to
obtain a product which meets the required properties, referred to
above, the proportions are important. Consequently there are
preferably from 20 to 50 ml of fillers b)+c) per 100 g of polymer
a), and the volume ratio of b) to c) is between 70/30 and
30/70.
[0085] Besides these components, which are necessarily present, the
adhesive of the invention may comprise one or more of the following
constituents:
[0086] Plasticizers, examples being organic esters, e.g.,
phthalates such as dioctyl phthalate or diisodecyl phthalate,
adipates such as dioctyl adipate, for example, polybutenes or other
compounds which are not reactive toward silanes, solvents, further
organic or inorganic fillers such as, for example, other calcium
carbonates, kaolines, aluminas, silicas, fibers, e.g., of
polyethylene, pigments, thickeners, e.g., urea compounds or
poly-amide waxes, heat stabilizers or UV stabilizers, adhesive
promoters, e.g., amino silanes or epoxy silanes, especially
H.sub.2N--(CH.sub.2).sub.3--Si(OCH.sub.3).sub.3,
H.sub.2N--(CH.sub.2).sub-
.2--NH--(CH.sub.2).sub.3--Si(OCH.sub.3).sub.3 or
NH--[(CH.sub.2).sub.3--Si (OCH.sub.3).sub.3].sub.2, dryers,
vinyltrimethoxy silane for example, catalysts, amine compounds for
example such as isophoronediamine or Jeffamines, for example, or
organotin compounds, such as dibutyltin laurate, dibutyltin
acetylacetonate for example, or other catalysts customary in
polyurethane chemistry, and also further substances normally used
in polyurethane sealants and adhesives.
[0087] As compared with the silane-crosslinking polyurethane
prepolymers the adhesives of the present invention have the
advantage that they are isocyanate-free and, by virtue of the
inventive combination of a special silane-crosslinking polyurethane
prepolymer, soot, and fine-particle coated calcium carbonate, are
suitable for applications requiring at one and the same time
tensile strengths of more than 4.5 MPa, elongations at break of
more than 250%, an electrical volume resistance of more than
10.sup.8 ohm cm, and good applicability. Examples of such
applications are the sealing and adhesive bonding of metallic
components, especially flexible adhesive bonding. The adhesives of
the invention are therefore, on the one hand, suitable for the
production of buses, trucks, and rail vehicles, and, on the other
hand, are even able to meet the requirements imposed on assembly
adhesives in the automobile industry.
[0088] The invention is illustrated below with reference to
examples which are not, however, intended in any way to restrict
it.
EXAMPLES
[0089]
1 Starting materials used: Polyol PPG 12000 Acclaim 12200 from
Bayer Plasticizer Diisodecyl phthalate, e.g. from BASF
Fine-particle coated Socal U1S2 from Solvay calcium carbonate Soot
Printex 60 from Degussa Huls Catalyst solution 90 parts by weight
diisodecyl phthalate 10 parts by weight dibutyltin dilaurate
[0090] Description of the Test Methods:
[0091] The extrusion force was determined in aluminum cartridges
having a diameter of 45 mm, the adhesive being pressed through an
opening of 5 mm at the tip of the cartridge. Extrusion took place
by means of a tensile testing machine, with recording of the
required force, at a rate of 60 mm/min.
[0092] The tensile strength and the elongation at break were
determined on cured films in a layer thickness of approximately 3
mm in accordance with DIN 53504 (S2). The electrical volume
resistance was measured at 1 000 V on cured films in a layer
thickness of approximately 3 mm in accordance with DIN 53482.
Example 1
[0093] Diethyl N-(3-trimethoxysilylpropyl)aspartate (Maleic Ester
Aminosilane Adduct)
[0094] 509.9 g .gamma.-aminopropyltrimethoxysilane were introduced
into a vessel. Subsequently 490.1 g of diethyl maleic were added
slowly, dropwise, and with thorough stirring at room temperature.
The temperature rise, caused by the exothermic reaction, was
arrested at 30.degree. C. by cooling in a waterbath. The mixture
was subsequently stirred at room temperature for 8 hours until the
reaction was at an end.
Example 2
[0095] Silane-Terminated Polyurethane Prepolymer
[0096] 1 000 g of polyol PPG 12000, 78.7 g of isophorone
diisocyanate, and 0.13 g of dibutyltin dilaurate were heated to
90.degree. C. with constant stirring and left at that temperature
until the free isocyanate group content reached a figure of 0.7%.
Subsequently 63.2 g of diethyl N-(3-trimethoxysilylpropyl)aspartate
from example 1 were mixed in and the mixture was stirred at
90.degree. C. for approximately 4 hours until free isocyanate could
no longer be detected by means of IR spectroscopy. Subsequently 0.4
g of silane A-171 was mixed in in order to scavenge residual
moisture, and the prepolymer was cooled to room temperature and
stored in the absence of moisture.
Examples 3 to 7
Inventive Adhesives
[0097] The ingredients of the individual examples were mixed
homogeneously in the order according to table 1 in a suitable
vacuum mixer, e.g., Planimax from Molteni. In a first step the
prepolymer, the plasticizer, and the fillers were homogenized, and
subsequently the additional silanes and the catalyst solution were
mixed in. The finished adhesives were filled into airtight
cartridges.
Examples 8 to 11
Adhesives Outside the Scope of the Invention
[0098] The preparation procedure is the same as for examples 3 to
7.
2TABLE 1 Composition of the adhesives (parts by weight) Example: 3
4 5 6 7 8 9 10 11 Prepolymer from example 2 100 100 100 100 100 100
100 100 100 Plasticizer 35 35 35 35 35 35 35 35 35 Fine-particle
coated 31.2 62.4 52 41.6 78 104 78 26 0 calcium carbonate Soot 32.4
28.8 36 43.2 36 0 18 54 72 Vinyltrimethoxysilane 2.5 2.5 2.5 2.5
2.5 2.5 2.5 2.5 2.5 N-.beta.-(aminoethyl)-.gamma.- 2.5 2.5 2.5 2.5
2.5 2.5 2.5 2.5 2.5 aminopropyltrimethoxysilane Catalyst solution
2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5
[0099]
3TABLE 2 Degree of filling of the adhesives per 100 g of polymer
Example: 3 4 5 6 7 8 9 10 11 Total filler volume 30 ml 40 ml 40 ml
40 ml 50 ml 40 ml 40 ml 40 ml 40 ml Calcium carbonate/ 40/60 60/40
50/50 40/60 60/40 100/0 75/25 25/75 0/100 soot ratio (by volume)
Inventive composition: Yes Yes Yes Yes Yes No No No No
[0100]
4TABLE 3 Properties of the adhesives Example: 3 4 5 6 7 8 9 10 11
Extrusion force 660 870 1100 1640 2000 240 510 3000 7000 [N]
Tensile strength 5.9 4.8 5.5 4.5 4.9 1.8 3.3 4.8 6.3 [MPa]
Elongation at 300 280 300 250 250 330 310 160 150 break [%]
Electrical volume 4.3 .times. 10.sup.10 3.1 .times. 10.sup.10 2.7
.times. 10.sup.10 1.2 .times. 10.sup.10 3.0 .times. 10.sup.11 1.3
.times. 10.sup.11 1.3 .times. 10.sup.11 1.4 .times. 10.sup.7 3.2
.times. 10.sup.5 resistance [ohm cm]
[0101] The inventive adhesives of examples 3 to 7 meet the required
properties, i.e., they have a tensile strength of at least 4.5 MPa,
an elongation at break of at least 250%, an electrical volume
resistance of at least 10.sup.8 ohm cm, an extrusion force of not
more than 2 000 N.
[0102] The adhesives from examples 8 to 11, which lie outside the
scope of the invention, do not meet all of the required properties.
Examples 8 and 9, which contain no soot or only a small fraction of
soot, have inadequate tensile strength. Examples 10 and 11, which
contain only a small fraction of coated calcium carbonate or none
at all, have an excessive extrusion force, an inadequate elongation
at break, and an electrical volume resistance which is too low.
[0103] Whereas the present application describes preferred
embodiments of the invention, it should clearly be pointed out that
the invention is not restricted to these embodiments and may also
be performed in other ways within the scope of the claims which
follow.
* * * * *