Note: Descriptions are shown in the official language in which they were submitted.
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ADDITION POLYMERIZABLE ISOCYANATE-POLYAMINE
~ ANAEROBIC ADHESIVES
;~ The instant invention relates to novel formu- lations useful as anaerobic adhesives.
~,
Anaerobic adhesives are well known and have
- been in commercial use for several years. Most anae-
robic adhesives are compositions containing a monomer,
; or combination of monomers, which will polymerize under
` certain conditions but not und~r other conditions.
`` Those conditions generally favoring polymerization
include the absence of oxygen cmd, i~ a redox initiator
is used, the presence of metal ions. Oxygen will act
as a polymerization inhibitor, and metal ions will act
'`! ~ as polymerization promoters.
':,' . :
~ Consequently, these adhesives find optimal
:
.~ use in situations where they are pressed tight between
`~ 15 two metal surfaces, such as between the threads of a
bolt and nut. The close fit effectively removes oxygen,
and the metal surface provides metal ions. This com-
bination of conditions causes the adhesive to polymerize,
and a strong bond results.
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Practical formula~ions often also contain
initiators, accelerators, stabilizers, thickeners,
plasticizers, diluents, chela-ting agents and~or adhe-
sion promoters.
This invention is directed to an anaerobic
adhesive comprising:
(a) The reaction product of:
(1) an addition polymerizable ethylenically
unsaturated isocyanate and
(2) a polyamine, wherein the reaction between
the polyamine and the isocyanate has
been carried out in the absence of an
added catalyst; and
(b) a polymerization initiator.
.,
This invention is also directed to a method
of bonding substrates at a bond site comprising placing
the above described adhesive at the bond site so as to
form a bond.
Suitable isocyanates include any readily
addition polymerizable ethylenically unsaturated mono-
isocyanate. Examples include vinyl isocyanate and
vinylbenzene isocyanate. Preferred are isocyanato
acrylates of the formula:
Rlo
" . ~,
`. "~ H2C-C-C-O-R2-N=C=O
wherein R1 is a hydrogen or a carbon chain of from 1 to
:
:
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5 carbon atoms and R2 is a carbon chain of rom 1 to 7
caxbon atoms. More preferred is 2-isocyanatoethyl
acrylate. Most preferred is 2-isocyanatoethyl meth~
acrylate (IEM).
The products of polyamines and isocyanates
- have an unusually long shelf life. Unlike other poly-
active hydrogen compounds, polyamines react readily
with isocyanate moieties, without the ne~d for added
catalyst. It is believed that this lack of catalyst in
the amine/isocyanate reaction contributes to the long
shelf life of these adhesives.
In this conte~t, "polyamine" is intended to
mean any polyac~ive hydrogen compound wherein an average
greater than one of the active hydrogen moieties is
provided by amine groups. A polyamine may generally be
illustrated by the formula:
R3 R4
H-N-R5-N-H
wherein R3 and R4 are each a hydrogen or an organic
group and R5 is an organic group. Aminated polyglycols
are examples of suitable polyamines. Other examples
include ethylenediamine, 1,4-butylenediamine, 1,2- and
1,3-diaminopropane, 1,7-diaminohexane, diaminobenzene
and diaminotoluene. Interestingly, experiments with
~` Jeffamine~ polyamines showed that polyamines with
higher molecular weight produced adducts with lower
viscosity.
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In formulating an adhesive according to the
; invention, the isocyanate and polyamine should be
reacted in a ratio such that the reactant is capable of
being addition polymerized to a substantially solid
material. Since suitable polyamines specifically
include those compounds having 3 or more active hydrogen
moieties per molecule, in defining reaction ratios it
is important to specify ~hether equivalent ratios or
molecular ratios are being used. It is generally
desirable, from a toxicological standpoint, to have a
slight excess of active hydrogen moiety. From an
adhesive standpoint, it is desirable to have at leas~ 1
molecule of isocyanate for each molecule of polyamine.
An excess of isocyanate is not unduly harmful to the
adhesive properties. Preferably, there should be about
one equivalent of isocyanate for each equivalent of
polyamine.
To be useful as an anaerobic adhesive, the
; isocyanate-polyamine reac~ion product requires a free
radical generating means capable of initiating addition
polymerization of the reaction product. Any free
radical generating means such as a peroxygen compound,
an azo compound, a W source and/or a heat source which
~ is suitably employed in the addition polymerization of
;~ 25 ethylenically unsaturated monomers is suitably employed
in the practice of this invention. Examples of such
free radical generating means and conditions of use are
set forth in U.S. Patent No. 3,043,820. Preferred free
radical generating means are chemical initiatars,
especially the peroxygen compounds such as hydrogen
peroxide and the entire class of organic peroxides and
.,
hydroperoxides such as cumene hydroperoxide and t-butyl
hydroperoxidP. Such initiators or other free radical
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generating means are employed in a curing amount, thatis, an amount sufficient to cause the desired polymeri-
zation of the reaction product. In ~he case of the
hydroperoxides, such are preferably employed in amounts
as low as 0.01 weight percent based on the weight of
the reaction product, more preferably from 1 to 10
weight percent.
Although not re~uired, it is often preferable
to employ an accelerator in combination with the initi-
ator. Accelerators are compounds which are believed toassist in the breakdown of the initiator and increase
the rate of initiator breakdown. Typical accelerators
include tertiary amines such as N,N'-dimethylaniline;
N,N'-dimethyl-p-toluidene; triethylamine; and imides
such as benzoic sulfimide. Such accelerators may be
used in quantities of 0.01 to 15 percent by weight,
based on the weight of initiator, with 0.1 to 7 percent
being preferred.
Metal ions are particularly effective and
~0 useful accelerators. While metal ions may be specifi-
cally added to the composition, a trace amount will
possibly be present as an impurity. In any event, if
the a &esive is applied to a metal substrate, the
substrate will provide the metal ion source. The
application of the adhesive to a metal is particularly
advantageous in that it delays the breakdown of the
initiator until the adhesive is actually being used.
Exa~ples of effective metal ions include Cu , Fe
Cr++ and V++. The metal ions need be present only in
catalytic (trace) amounts.
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Because the aforementioned initiators or
combination of initiator and accelerators promote
polymerization quite well, it is generally required to
employ an inhihitor to prevent premature polymerization.
~xamples of such inhibitors are antioxidants including
phenols such as 2,6-di-tert-butyl-4-methylphenol (Ionol~),
quinones such as benzoquinone, hydroquinones and other
compounds that are known to inhibit addition polymeriza
tion of ethylenically unsaturated monomers.
An effective amount of an inhibitor must be
added to a useful adhesive formulation. An "effective
amount" of an inhibitor is an amount which will prevent
premature polymerization of the formulation. Excess
inhibitor will cause long cure times. Preferably, the
inhibitor is a quinone or a hydroquinone which is
preferably employed in an amount in the range from 5 to
10,000 ppm based on the formulation weight, more prefer-
ably from 50 to 1,000 ppm~
While a ree-radical initiatox is, in practi-
cal terms, a requirement, the other components of theinitiator system are optional. ',ome applications will
need none or only some of the other ingredients, but
others will require all of them.
The adhesive of the instant invention is
2~ utilizable in a num~er of applications. Uses include
adhesives and metal impregnation. Specific applica-
tions include locking threaded assemblies, sealing
threaded, porous and flanged assemblies, strengthening
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cylindrical assemblies and structural bonding. Sub-
strates to be bonded include metals, plastics, ceramics
and glass. Potential medical applications include
tooth and bone cementing sealants.
In applications such as locking the threads
of steel bolts and nuts, the oxygen which is present in
the adhesive is quickly consumed by the initiator, and
the physical barrier of the threads prevents the infu-
sion of new oxygen. In other applications or in parti-
cular formulations, however, it may be desirable to
specifically remove the oxygen from the system. Such
removal may be by mechanical means such as a vacuum
pump or by chemical means such as an oxygen consuming
agent.
Further details of the invention will become
apparent in the following examples. In the examples,
all percentages are by weight, unless otherwise speci-
fied.
PREPARATION OF IEM ADDUCT
IEM-Ethylenediamine Adduct
Ethylenediamene (60.0 g, 2 equivalents active
hydrogen) and Ionol~ antioxidant (O.15 g) were combined
in a reaction vessel. The mixture was at room tempera-
ture and IEM (194 g, 1.9 moles) was added over a 1-hour
period. The temperature rose to 125C. The final
product was a solid which will not melt at 125C.
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Example 1
Shelf Stability of IEM-Poly~ine Adduct Formulation
Jeffamine~ D400 polyamine, available from
Jefferson Chemical Co., (120.24 g, dried over a molecu-
lar sieve3 was blended with 0.11 g Ionol~ inhibitor.
The amine was added dropwise to the IEM at a rate such
that the temperature of the reaction mixture did not
exceed 50C. An infrared spectograph showed that the
reaction was complete. The product was a translucent
amber viscous liquid. Accelerated aging tests showed
the product to have excellent shelf stability.
The procedure was repeated except that the
temperature was not allowed to exceed 30C. The results
were slmllar.
The first reaction product was formulated
with 2.0 percent cumene hydroperoxide and 500 ppm
Ionol~. When placed in an 82C bath, the formulation
gelled in 20 minutes.
Comparative Run A
Shelf Stability of IEM-Po~yol Adhesive Formulation
IEM (145.2 g) was reacted with tetraethylene
glycol (90.0 g) in the presence of 0.235 g zinc octoate
and a total of 00227 g Ionol~ and 0.225 g Da~co~ (tri-
ethylenediamine). A~ in Example 1, the product was
formulated with 2.0 percent cumene hydroperoxide and
500 ppm Ionol~. This formulation gelled in less than 3
minutes when placed in an 82C bath.
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