Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-11-24
2001-05-15
Gallagher, John J. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C526S313000, C526S320000, C526S329600
Reexamination Certificate
active
06231714
ABSTRACT:
BACKGROUND OF THE INVENTION
It is known from U.S. Pat. No. 5,084,490 and U.S. Pat. No. 5,141,970 that cationically cured propenyloxystyrene monomers have outstanding thermal and mechanical properties. The monomers undergo a 2-stage curing process involving an initial acid catalyzed addition polymerization or copolymerization of the styrene group (A-stage), followed by a heat-triggered post-curing reaction of the propenyloxyphenyl group (B-stage). During the post curing reaction, the A-stage polymer rearranges to form a reactive phenolic polymer, which spontaneously reacts with the propenyloxy group via an electrophilic substitution reaction. This results in the formation of a highly crosslinked polymer that exhibits a high decomposition temperature (T
d
>400° C., TGA), a high glass transition (T
g
>300° C., DMA) and good adhesion.
U.S. Pat. No. 5,369,200, Schädeli et al. (1994), describes terpolymers of two different maleimide monomers and an olefinically unsaturated phenyl ether monomer in which the phenyl ether is defined by an acid cleavable group —OR
2
linked to a phenyl ring. Examples of such monomers in this reference include a terpolymer of 4-(2-tetrahydropyranyloxy)benzyl methacrylate, N-hydroxymethylmaleimide and N-(acetoxymethyl)maleimide. The terpolymers are used as positive resists with acid generating photocatalysts and therefore it is imperative that the —OR
2
group be selected to be acid cleavable.
U.S. Pat. No. 5,211,877, Andrejewski et al, (1993) and U.S. Pat. No. 5,641,850 (Stoher et al) describe liquid-crystalline polyorganosiloxanes containing (meth)acryloxy groups. Also described are the monomers 4-(prop-2-ene-1-oxy)benzoic acid 4-methacryloxyphenyl ester and 4-(prop-2-ene-1-oxy)benzoic acid 4-(4-methacryloxybiphenyl)ester,
U.S. Pat. No. 4,468,524, Zahir and U.S. Pat. No. 4,387,204, Zahir describe alkenylphenyl substituted acrylates or methacrylates and crosslinkable monomer compositions employing same.
Anaerobically curable compositions are a well known class of curable (meth)acrylate monomers composition. The compositions typically include polyfunctional monomers such as polyethylene glycol dimethacrylate (PEGMA), although some systems based on mono(meth)acrylates are known. The compositions also include a free radical catalyst system which is stabilized by atmospheric oxygen. The catalyst system usually include a hydroperoxide catalyst, typically cumene hydroperoxide, and at least one accelerator. Benzenesulfimide (saccharin) is a typical accelerator. Other common accelerators include acetyl phenyl hydrazine and dimethyl-para-toluidene. Deprivation of oxygen characteristically initiates cure (although initiation frequently also requires an additional condition to be simultaneously met, such as the provision of a source of metal ions or of heat). Anaerobically curable compositions are widely used as thread lockers, pipe joint sealants, gasketing agents, adhesives and as impregnation resins. To achieve a storage stability which is balanced based on access to atmospheric oxygen, other stabilizers are conventionally included in the composition.
It would be desirable to have anaerobically curable compositions which have improved high temperature resistance, especially a heat resistance capability comparable to the heat resistance of the B-staged cationically cured propenyloxystyrene monomer compositions described in U.S. Pat. No. 5,084,490 and U.S. Pat. No. 5,141,970.
SUMMARY OF THE INVENTION
The present invention pertains to curable formulations of monomers characterized as having both (meth)acrylic ester functionality and allylic phenyl ether functionality on the same molecule and the phenyl ring having at least one unblocked position ortho or para to the allylic ether group. Such compositions give high strength adhesive bonds when cured by a free radical mechanism. Further, the cured compositions are capable of thermally induced Claisen rearrangement, with or without an acid catalyst, thereby substantially improving the thermal stability of the cured polymer. A particularly surprising feature of the invention is that anaerobically curable compositions can be formulated using such monomers which give anaerobically cured adhesive bonds comparable to, or stronger than conventional anaerobic formulations based on multi-methacrylate monomers such as polyethylene glycol dimethacrylate (PEGMA).
One aspect of the invention therefore is a curable formulation comprising:
a) at least one monomer compound having both (meth)acrylic ester functionality and an allylic phenyl ether functional group on the same molecule, the allylic phenyl ether functional group having at least one unsubstituted position on the phenyl ring which is ortho or para to the allylic ether group, and
b) a free radical catalyst system.
In certain embodiments the free radical catalyst is a free radical photoinitiator or an anaerobic curing catalyst system. The formulation may also include a latent thermally activated acid generator.
Another aspect of the invention comprises a method for bonding a pair of substrates, the method comprising:
i) applying a composition to a first of said substrates, the composition comprising:
a) at least one monomer compound having both (meth)acrylic ester functionality and allylic phenyl ether functionality on the same molecule, the allylic phenyl ether functional group having at least one unsubstituted position on the phenyl ring which is ortho or para to the allylic ether group, and
b) an anaerobic curing catalyst system or a free radical photoinitiator system;
ii) joining a second substrate to the first substrate with the applied formulation therebetween so as to induce anaerobic curing of the applied formulation and form a bonded assembly; and subsequently
iii) subjecting the bonded assembly to an elevated temperature of at least 100° C., preferably at least 150° C.
Yet another aspect of the invention comprises a method of preparing an anaerobically curable monomer comprising:
i) etherifying a phenolic hydroxyl group of a dihydroxybenzene or a phenol alcohol with an allylic etherifying agent, to give a hydroxy-substituted allylic phenyl ether compound; and then
ii) esterifying said hydroxy-substituted allylic phenyl ether compound with an acrylic or methacrylic acylating agent.
Novel monomers useful in the formulations described above are a further aspect of the invention. Such compounds are characterized by formulas I and II:
where R
1
is H or methyl; R
2
is a direct bond, a group of the formula —C
2
H
2n
—, or a group of the formula —(OC
n
H
2n
—)
m
which when taken with the phenyl group to which it is attached forms a phenyl ether; n is 1-4; m is 1-10; R
3
is —CH
2
CH═CH
2
, —CH
2
C(CH
3
)═CH
2
, —CH
2
CH═CH(CH
3
), —CH
2
C(CH
3
)═CH(CH
3
), —CH
2
CH═C(CH
3
)
2
or —CH
2
CH═CH(C
6
H
5
); and R
4
is a divalent allylic group, and wherein the compound is optionally substituted on a phenyl group thereof by an alky, alkoxy or halo group, provided that relative to the respective —OR
3
or —OR
4
O— groups, at least one unsubstituted ortho or para position remains on an adjacent phenyl ring. Polymers produced from such monomers, curable compositions employing such polymers, and methods for producing such polymers comprise further aspects of the invention.
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McArdle Ciaran B.
Morrill Susanne
Woods John G.
Gallagher John J.
Loctite Corporation
Vidas Arrett & Steinkraus
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