Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-07-24
2003-02-11
Medley, Margaret (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S583000, C523S160000, C523S303000, C428S343000, C428S344000, C428S3550AC, C428S3550EN, C381S150000, C435S808000
Reexamination Certificate
active
06518356
ABSTRACT:
The present invention relates to an aerobically curing reactive adhesive composition and to its preparation and use.
Adhesive bonds are encountered in the domestic appliance, electrical, electronics, furniture, sports goods, construction (interior and exterior), ceramics and automotive industries, including their supplier operations. The mechanical engineering sector profits from the adhesive properties in the same way as does valve or installation engineering, where additionally there are sealing functions to be undertaken. In addition to same-kind material combinations of steel, aluminum, brass, copper, coated metal surfaces, wood, glass, PVC, PC (polycarbonate), and ABS, pairings of different materials are of particular importance from the standpoint of adhesives technology. In the case of these composite bonds, differences in thermal expansion behavior, or loss of adhesion, which occurs inter alia on materials such as ferrite or ceramic, often mean that the performance limit of known adhesive systems is reached. In certain applications, the adhesives are further required to possess damping properties, and/or in the case of different electrochemical potentials must not have any corrosion-promoting properties.
Known adhesive systems such as 2-part epoxy resins, cyanoacrylates, dispersion adhesives, contact adhesives, 2-part acrylate adhesives, 2-part poly-urethane adhesives or anaerobically curing adhesives are known to have performance limits in terms of gap-filling capacity, elasticity, automatic metering, heat stability, volatility, and aging.
Furthermore, for the bonding of a very wide variety of materials in the context of automated industrial manufacture, the demand is predominantly for short cycle times. Aerobically curable adhesives, as are known, for example, from DE-A-4000776 or DE-A-4123194, meet many of the abovementioned requirements. As is known, aerobically curable adhesive compositions are free-radically polymerizable multi-substance mixtures which are stable on storage to the exclusion of air, especially to the exclusion of oxygen. Furthermore, these compositions are required to contain no peroxides. For this purpose, as is known, these compositions are thoroughly degassed, and/or a deoxygenator is added to them. This enables a controlled initiation of polymerization: for example, adhesives and sealing, coating and molding compounds are initially stable on storage for a period of several months, which is sufficient for practical purposes, and then cure simply within a short time even at room temperature when air is admitted. Activation of the aerobic adhesive requires waiting times, before or after joining, during which the oxygen of the air must have access to the adhesive composition. For automatic industrial manufacture with its short cycle times, DE-A-4441414 proposes apparatus and measures for the metering and storage of aerobic adhesives. According to the teaching of the document, the time between application of the adhesive and joining of the parts to be connected may also be reduced by adding the oxygen to the adhesive even before the latter is applied. To this end, the application device comprises a mixing chamber in which the oxygen—whether in pure form or as air—is added to the adhesive under greater or lesser pressure.
For activation, one-component aerobically curing reactive adhesives require a certain time in order to take up atmospheric oxygen (air contact time). The air contact time required is dependent on the additives and stabilizers used in the adhesive composition, on temperature and on other parameters, so that for the user it is first necessary to determine the particular optimum air contact time by means of experiments. For unproblematic and low-error application of such adhesives, therefore, there is a need to be able to determine, simply, the sufficient uptake of oxygen by the aerobically curable composition.
The solution provided by the invention to this problem is given in the claims. It consists essentially in the provision of aerobically curable compositions which are based on free-radically polymerizable compounds and comprise an activator system for forming peroxides and a dye as an indicator of sufficient oxygen uptake. Furthermore, the aerobically curing compositions of the invention may comprise further customary additives.
The addition of dyes to adhesive compositions for the purpose of monitoring the degree of curing is already known. For instance, EP-A-342965 describes an adhesive composition comprising a one-component heat-curing adhesive and an effective fraction of a water-insoluble indicator which does not react with the components of the adhesive at room temperature but which on heat curing produces a color change to enable a visible determination of the state of cure of the adhesive.
EP-A-79703 describes a two-component adhesive composition whose first component comprises a vinyl monomer and a polymerization initiator and whose second component comprises a polymerization accelerator, and additionally a redox indicator having an E
o
of greater than +0.01 to less than +0.76 volt and an R
H
of from 13.5 to 28. According to the teaching of this document, the dye serves to indicate the time from which the mixture of the two-component adhesive composition, after mixing, should no longer be used (end of pot life). This dye further serves to distinguish the two reactive components and to ascertain the completeness of mixing.
DE-A-4001417 describes a toughened two-component epoxy resin adhesive based on an epoxy resin and on an amine hardener, the resin component comprising a color indicator which indicates the homogenous mixing of resin and hardener by means of a change in color.
DE-A-4132726 and DE-A-4112649 describe adhesive systems based on epoxy resins to which a color or, respectively, a color pigment is admixed which changes its color on curing, so making it possible to determine complete curing of the adhesive composition.
EP-A-96500 describes a two-component adhesive composition based on polymerizable vinyl monomers, free-radical stabilizers, and a free-radical curing system. When the two components are mixed a color change takes place which allows for complete mixing and represents a visible indicator of the limited pot life. Additionally, the curing process is accompanied by a color change.
None of the abovementioned documents discloses an indicator for the sufficient oxygen uptake of aerobically curable adhesive compositions.
The free-radically polymerizable compounds of the present invention comprise
A) at least one polyurethane (meth)acrylate of the general formula
[H
2
C═CR
1
—C(═O)—O—R
2
—O—C(═O)—NH—]
n
R
3
(I)
in which
R
1
=hydrogen or a methyl group
R
2
=a linear or branched alkyl group having 2 to 6 carbon atoms or alkylene oxides having 4 to 21 carbon atoms,
n=2 or 3, and
R
3
if n=2 is:
[—Q—NH—C(═O)]
2
[{—O—R
4
—O—C(═O)—NH—Q′—NH—C(═O) }
m
—O—R
4
—O—]
in which m=0 to 10,
R
4
is
a) a polycaprolactonediol radical,
b) a polytetrahydrofurfuryldiol radical or
c) a diol radical derived from a polyester diol characterized by a C:O ratio of >2.6, a C:H ratio of <10, and a molecular weight from 1000 to 20,000, or
d) a diol radical derived from a polyester diol which is liquid at 20° C. and has a molecular weight of from 4000 to 10,000, measured with the aid of GPC (gel permeation chromatography), and
R
3
if n=3 is:
[—Q—NH—C(═O)—O—((CH
2
)
5
—C(═O)
p
—]
3
R
5
in which R
5
is a triol radical of a linear or branched trivalent alcohol containing 3 to 6 carbon atoms and p is from 1 to 10, and
Q and Q′, independently of one another, are aromatic, aliphatic or cycloaliphatic groups which contain 6 to 18 carbon atoms and are derived from diisocyanates or mixtures of diisocyanates, and also
B) one or more (meth)acrylate comonomers, where said composition comprises 20-80% by weight of the polyurethane (meth)acrylate, and 80-
Friese Carsten
Knuebel Georg
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Medley Margaret
Seifert Arthur G.
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