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Curable composition and compatibilizing agent

Curable composition and compatibilizing agent description/claims

The present invention relates to a curable composition comprising a crosslinkable functional group-containing vinyl polymer and a crosslinkable functional group-containing polyether polymer and to a compatibilizing agent for compatibilizing the above polymers with each other.

Unlike polymers obtainable by ionic polymerization or polycondensation, functional group-containing vinyl polymers, in particular functional group-terminated vinyl polymers, obtain able by radical polymerization have scarcely been put to practical use. Among vinyl polymers, (meth)acrylic polymers have such characteristics as high weatherability and transparency that polyether polymers, hydrocarbon polymers or polyester polymers cannot have, and (meth)acrylic polymers having an alkenyl or crosslinking silyl group(s) on a side chain(s) are currently used in highly weather-resistant coating compositions and the like. On the other hand, it is not easy to control the polymerization of acrylic polymers because of side reactions, and it is very difficult to introduce a functional group into such polymers at one or both ends.

If vinyl polymers having an alkenyl group at a molecular chain terminus or termini can be obtained by a simple and easy method, it becomes possible to obtain cured products superior in cured product physical properties to cured products from vinyl polymers having a crosslinking group(s) on a side chain(s). Therefore, a number of researchers have so far made investigations concerning the method for the production thereof. However, it is not easy to produce them on a commercial scale. In Japanese Kokai Publication Hei-01-247403 and Japanese Kokai Publication Hei-05-255415, for instance, there is disclosed a method of synthesizing alkenyl-terminated (meth)acrylic polymers which uses an alkenyl group-containing disulfide as a chain transfer agent.

Japanese Kokai Publication Hei-05-262808 discloses a method of synthesizing alkenyl-terminated (meth)acrylic polymers which comprises synthesizing a vinyl polymer having a hydroxyl group at each end using a hydroxyl group-containing disulfide and further utilizing the reactivity of each hydroxyl group.

Japanese Kokai Publication Hei-05-211922 discloses a method of synthesizing silyl group-terminated (meth)acrylic polymers which comprises synthesizing a vinyl polymer having a hydroxyl group at each end using a hydroxyl group-containing polysulfide and the reactivity of each hydroxyl group.

These methods can hardly ensure that a desired functional group will be introduced at each of both ends. Hence, cured products having satisfactory characteristics cannot be obtained. For introducing a functional group at each of both ends without fail, a chain transfer agent must be used in large amounts, and this is a problem from the production process viewpoint. In addition, these methods use an ordinary method of radical polymerization, so that it is difficult to control the molecular weight and molecular weight distribution (ratio of weight average molecular weight to number average molecular weight) of the product polymer.

In view of such a state of the art, the present inventors have so far made a number of inventions relating to various crosslinkable functional group-terminated vinyl polymers, methods of producing the same, curable compositions comprising the same, and uses thereof (cf. Japanese Kokai Publication Hei-11-080249, Japanese Kokai Publication Hei-11-080250, Japanese Kokai Publication Hei-11-005815, Japanese Kokai Publication Hei-11-116617, Japanese Kokai Publication Hei-11-116606, Japanese Kokai Publication Hei-11-080571, Japanese Kokai Publication Hei-11-080570, Japanese Kokai Publication Hei-11-130931, Japanese Kokai Publication Hei-11-100433, Japanese Kokai Publication Hei-11-116763, Japanese Kokai Publication Hei-09-272714, and Japanese Kokai Publication Hei-09-272715, among others).

For example, vinyl polymers having a silicon-containing group comprising hydroxyl or hydrolyzable group(s) bound to a silicon atom and capable of crosslinking under siloxane bond formation (herein after, such silicon-containing group is also referred to as “crosslinkable silyl group”) or cured products obtain able from compositions comprising the same are excellent in heat resistance and weatherability and can be used in various fields of application which include, but are not limited to, sealing materials, for example sealing materials such as elastic sealing materials for building and construction and sealing materials for laminated glass, electric and electronic part materials such as solar cell back sealers, electric insulating materials such as wire/cable insulating sheath, pressure sensitive adhesive materials, adhesives, elastic adhesives, paints, powder paints, coating compositions, foamed bodies, potting materials for electric and electronic use, films, gaskets, casting materials, various molding materials, and rustproof and waterproof sealants for end faces (cut sections) of net glass or laminated glass.

On the other hand, polyether polymers having at least one crosslinking silyl group are disclosed, for example, in Japanese Kokoku Publication Sho-45-36319, Japanese Kokoku Publication Sho-46-12154, Japanese Kokoku Publication Sho-46-30741 and Japanese Kokoku Publication Sho-49-32673, Japanese Kokai Publication Sho-50-156599, Japanese Kokai Publication Sho-51-73561, Japanese Kokai Publication Sho-54-6096, Japanese Kokai Publication Sho-55-13767, Japanese Kokai Publication Sho-55-13768, Japanese Kokai Publication Sho-55-82123, Japanese Kokai Publication Sho-55-123620, Japanese Kokai Publication Sho-55-125121, Japanese Kokai Publication Sho-55-131021, Japanese Kokai Publication Sho-55-131022, Japanese Kokai Publication Sho-55-135135 and Japanese Kokai Publication Sho-55-137129, and Japanese Kokai Publication Hei-03-72527 and Japanese Kokai Publication Hei-03-97825. When cured, they give high elongation cured products and therefore are used in elastic sealing materials and the like mainly intended for use in building and construction.

However, these polyethers, in particular polyethers having a main chain comprising a polypropylene oxide, have a problem in that hydrogen atoms each bound to a tertiary carbon atom are readily oxidized, hence the weatherability becomes poor, if no antioxidant is used. To solve this problem, the present inventors have already proposed, in Japanese Kokoku Publication Hei-02-42367 and Japanese Kokoku Publication Hei-02-44845, a curable composition improved in weatherability as a result of blending an acrylic polymer having at least one crosslinkable silyl group with a polyether polymer having at least one crosslinkable silyl group. Further, Japanese Kokoku Publication Hei-04-69667, there is disclosed a sealing material composition comprising a blend of an acrylic polymer having an alkoxysilyl group at each of both molecular ends as produced by using a chain transfer agent with a polyether polymer having an alkoxysilyl group at each of both molecular ends.

That vinyl polymer having at least one crosslinkable functional group which is to be blended with the polyether polymer having at least one crosslinkable functional group is generally produced by using a crosslinkable functional group-containing radical polymerization initiator or chain transfer agent. Therefore, it is difficult to attain a high percentage of crosslinkable functional group introduction at both ends. As a result, there arises a problem, namely the gel fraction of cured products decreases.

On the other hand, the combined use of a crosslinkable functional group-containing monomer is required for obtaining cured products with a satisfactory gel fraction. In this case, a problem arises, namely the high elongation characteristics intrinsic in polyether polymers are impaired. In this case, the elongation at break, in particular, decreases and, accordingly, the range of application of the composition in question is drastically restricted. Therefore, in using the same as a sealing material, improvements in weatherability can be attained only by sacrificing some or other physical characteristic(s), for example increase in modulus, decrease in elongation, worsening of residual tack, decrease in gel fraction, etc. In addition, the (meth)acrylic polymer used there is a product synthesized by free radical polymerization and, therefore, has a broad molecular weight distribution and a high viscosity, causing a problem that the mixture thereof with a polyether polymer also shows a high viscosity.

Concerning this problem, Japanese Kokai Publication Hei-11-116763 proposes to obtain a curable composition high in gel fraction and excellent in weatherability, without impairing the high elongation characteristic intrinsic in a crosslinkable functional group-containing polyether polymer, by using a low-viscosity vinyl polymer having a terminal crosslinkable functional group introduced thereinto with a high percentage. In this case, however, the compatibility of the two polymers may be poor in certain instances according to the molecular weight and molecular weight distribution of the vinyl polymer and/or polyether polymer and to the blending ratio of these two polymers. In that case, the curable composition resulting from blending, when stored for a long period of time, may undergo phase separation, for instance, hence the storage stability thereof may deteriorate. Furthermore, cured products obtainable from a composition with insufficient compatibility are inferior in homogeneity, so that good mechanical and physical properties may not be realized.

It is an object of the present invention to provide a curable composition which comprises a crosslinkable functional group-containing vinyl polymer and a crosslinkable functional group-containing polyether polymer and which has good storage stability and can give cured products retaining the high elongation characteristic originating from the polyether polymer and showing a high gel fraction and good weatherability.

Thus, the present invention provides a curable composition

which comprises the following two components:

(I) a polyether polymer having at least one crosslinkable functional group and (II) a vinyl polymer

• Provisional Patent
• Utility Patent

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