Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-04-27
2002-06-18
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S100000, C522S111000, C522S122000, C522S134000, C522S143000, C522S148000, C522S172000, C526S273000, C528S033000
Reexamination Certificate
active
06407146
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a curable composition modified with a vinyl polymer having at least one crosslinkable silyl group. More particularly, it relates to a curable composition which when blended with an epoxy resin, gives a composition capable of firmly adhering to various substrates and showing elastic properties after curing and useful, in particular, as an elastic adhesive and to a curable composition which when blended with a polyether polymer having at least one crosslinkable silyl group, gives a composition showing, after curing, a high elongation and good weathering resistance.
BACKGROUND ART
Epoxy resin-based adhesives are widely used in various fields of industry, for example in automobile, vehicle, airplane, ship building, electronics, building and civil engineering industries, owing to those reliable bond strength and durability characteristics which they show when applied to a wide variety of materials such as metals, plastics, wood, glass, ceramics, stone and concrete.
However, cured products thereof are generally high in modulus of elasticity and low in energy absorbing ability and therefore possess the drawback of being hard and brittle. Therefore, problems still exist in adhesion of materials greatly differing in coefficient of linear expansion or adhesion of building materials or like members subject to repeated displacements owing to heat cycles. For solving these problems, the so-called modified silicone-based elastic adhesives have become widely used which are blends of an epoxy resin and a polyether polymer having at least one crosslinkable silyl group.
Such polyether polymers having at least one crosslinkable silyl group are disclosed, among others, in Japanese Kokoku Publications Sho-45-36319, Sho-46-12154, Sho-46-30741 and Sho-49-32673; Japanese Kokai Publications Sho-50-156599, Sho-51-73561, Sho-54-6096, Sho-55-13767, Sho-55-13768, Sho-55-82123, Sho-55-123620, Sho-55-125121, Sho-55-131021, Sho-55-131022, Sho-55-135135, Sho-55-137129, Hei-03-72527 and Hei-03-97825. When cured, such polymers give cured products showing high elongation and are used mainly in elastic sealing compositions for architectural use, among others. However, these polyethers, in particular polyethers whose main chain is a polypropylene oxide, have a problem: without the use of an antioxidant, the hydrogen atom bound to a tertiary carbon atom is susceptible to oxidation, by which the weathering resistance is weakened. To solve this problem, the present inventors have already proposed in Japanese Kokoku Publication Hei-02-42367 and Japanese Kokoku Publication Hei-02-44845 curable compositions improved in weathering resistance which comprise a polyether polymer having at least one crosslinkable silyl group as blended with an acrylic polymer having at least one crosslinkable silyl group. Further, in Japanese Kokoku Publication Hei-04-69667, there is disclosed a sealing composition comprising a blend of an acrylic polymer having an alkoxysilyl group at both molecular termini and a polyether polymer having an alkoxysilyl group at both molecular termini.
However, the elastic adhesives mentioned above which comprise a blend of an epoxy resin and a polyether polymer have various problems. First, the epoxy resin and the crosslinkable silyl-containing polyether polymer are poor in compatibility. Thus, while it is generally possible to obtain a soft elastomer having a structure such that an epoxy resin is finely dispersed in the matrix of a polyether polymer, a hard type elastomer in which a polyether polymer is conversely dispersed in an epoxy resin matrix cannot be obtained. In addition, it is generally impossible to use the polyether polymer, which has a tertiary hydrogen atom in its main chain structure, in those fields in which weathering resistance and heat resistance are required.
To solve these problems, an epoxy-polyether-(meth)acrylic ternary system has been proposed in which a crosslinkable silyl-containing (meth)acrylic polymer having good weathering resistance and good compatibility with the epoxy resin is blended as a third component (Japanese Kokai Publication Hei-02-214759). However, the (meth)acrylic polymer used therein is a polymer synthesized by free radical polymerization and, therefore, has a wide molecular weight distribution and a high viscosity, so that the mixture thereof with an epoxy resin also has a high viscosity. Another problem is that since it is impossible to attain a high degree of crosslinkable silyl group introduction, the elastic properties once obtained are damaged by blending of a polyether polymer.
Accordingly, the present invention has for its object to provide a curable composition having low viscosity and capable of providing a wide variety of rigid and non-rigid elastomers having no more hard and brittle properties and improved in weathering resistance level while maintaining the adhesion strength of the epoxy resin.
The vinyl polymer having at least one crosslinkable silyl group, which is to be blended with a polyether polymer having at least one crosslinkable silyl group, is generally produced by using a crosslinkable silyl-containing radical initiator or chain transfer agent. Therefore, there is a problem that it is difficult to introduce a crosslinkable silyl group at both termini at a high rate and, therefore, the cured products tend to have a low gel fraction. For obtaining cured products with a sufficient gel fraction, it is necessary to combinedly use a crosslinkable silyl-containing monomer. In that case, however, there is the problem that the high elongation characteristics intrinsic in polyether polymers are damaged. In particular, the elongation at break becomes decreased, so that the range of use of the resulting composition is considerably restricted. Thus, for improving the weathering resistance of such composition for use as a sealing material, some physical properties must be sacrificed, resulting in an increased modulus, decreased elongation, worsened residual tack or lowered gel fraction. There is a further problem that the molecular weight distribution is broad and the polymer has a high viscosity because of the use of free radical polymerization.
In the art, it is not easy to produce a vinyl polymer having at least one crosslinkable silyl group with a high degree of crosslinkable silyl group introduction. The present invention is to provide a curable composition having a high gel fraction and good weathering resistance without impairing the high elongation and other properties intrinsic in crosslinkable silyl-containing polyether polymers by using a vinyl polymer having a low viscosity and a high degree of crosslinkable silyl group introduction.
It was found that the above problems can be solved when a curable composition comprises, as essential components, a vinyl polymer having at least one crosslinkable silyl group and an epoxy resin or a polyether polymer having at least one crosslinkable silyl group. This finding has now led to completion of the present invention.
SUMMARY OF THE INVENTION
The present invention provides a curable composition which comprises the following two components: (I) a vinyl polymer having at least one crosslinkable silyl group represented by the general formula (1) given below, and (II) an epoxy resin or a polyether polymer having at least one crosslinkable silyl group;
—[Si(R
1
)
2−b
(Y)
b
O]
m
—Si(R
2
)
3−a
(Y)
a
(1)
wherein R
1
and R
2
each represents an alkyl group containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon atoms, an aralkyl group containing 7 to 20 carbon atoms, or a triorganosiloxy group represented by the formula (R′)
3
SiO—, in which R′ represents, a monovalent hydrocarbon group containing 1 to 20 carbon atoms and the three R's may be the same or different, and when there are two or more R
1
or R
2
groups, they may be the same or different; Y represents a hydroxy group or a hydrolyzable group and, when there are two or more Y groups, they may be the same or different; a represents
Fujita Masayuki
Kusakabe Masato
Nakagawa Yoshiki
Connolly Bove Lodge & Hutz
Kaneka Corporation
McClendon Sanza L.
Seidleck James J.
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