| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | August 31, 2004 |
| PATENT TITLE |
Curable composition |
| PATENT ABSTRACT |
The invention relates to a curable composition comprising a crosslinking silyl-containing vinyl polymer. The curable composition of the invention can be utilized, for example, as sealants such as elastic sealants for building and construction, electric or electronic part materials such as solar battery backside sealants, electric insulating materials such as insulating sheath of wire or cable, pressure sensitive adhesives, adhesives, and paints. A curable composition which comprises the following two components: (A) a vinyl polymer (I) having at least one crosslinking functional group and (B) heavy or ground calcium carbonate (II) having a specific surface area of not smaller than 1.5 m.sup.2 /g but not larger than 50 m.sup.2 /g. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | November 12, 2002 |
| PATENT CT FILE DATE | December 22, 2000 |
| PATENT CT NUMBER | This data is not available for free |
| PATENT CT PUB NUMBER | This data is not available for free |
| PATENT CT PUB DATE | August 2, 2001 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A curable composition which comprises the following two components: (A) a vinyl polymer (I) having at least one crosslinking functional group and (B) heavy or ground calcium carbonate (II) having a specific surface area of not smaller than 1.5 m.sup.2 /g but not larger than 50 m.sup.2 /g, said specific surface area being measured using the air permeation method. 2. The curable composition according to claim 1, wherein the vinyl polymer (I) has a molecular weight distribution value of less than 1.8. 3. The curable composition according to claim 1, wherein the main chain of the vinyl polymer (I) is one produced by polymerizing a monomer selected from the group consisting of (meth)acrylic monomers, acrylonitrile monomers, aromatic vinyl monomers, fluorine-containing vinyl monomers and silicon-containing vinyl monomers as a main monomer. 4. The curable composition according to claim 1, wherein the vinyl polymer (I) is a (meth)acrylic polymer. 5. The curable composition according to claim 1, wherein the vinyl polymer (I) is an acrylic polymer. 6. The curable composition according to claim 5, wherein the vinyl polymer (I) is an acrylic ester-based polymer. 7. The curable composition according to claim 6, wherein the vinyl polymer (T) is a butyl acrylate-based polymer. 8. The curable composition according to claim 1, wherein the crosslinking functional group of the vinyl polymer (I) is a crosslinking silyl group. 9. The curable composition according to claim 1, wherein the crosslinking functional group of the vinyl polymer (I) is an alkenyl group. 10. The curable composition according to claim 1, wherein the crosslinking functional group of the vinyl polymer (I) is a hydroxyl group. 11. The curable composition according to claim 1, wherein the crosslinking functional group of the vinyl polymer (I) is an amino group. 12. The curable composition according to claim 1, wherein the crosslinking functional group of the vinyl polymer (I) is a group having a polymerizable carbon-carbon double bond. 13. The curable composition according to claim 1, wherein the crosslinking functional group of the vinyl polymer (I) is an epoxy group. 14. The curable composition according to claim 1, wherein the main chain of the vinyl polymer (I) is one produced by living radical polymerization. 15. The curable composition according to claim 14, wherein the living radical polymerization consists in atom transfer radical polymerization. 16. The curable composition according to claim 15, wherein the atom transfer radical polymerization uses, as a catalyst, a complex selected from transition metal complexes having, as the main metal, an element of the group 7, 8, 9, 10 or 11 of the periodic table of the elements. 17. The curable composition according to claim 16, wherein the metal complex used as the catalyst is a complex selected from the group consisting of complexes of copper, nickel, ruthenium or iron. 18. The curable composition according to claim 17, wherein the metal complex used as the catalyst is a copper complex. 19. The curable composition according to claim 1, wherein the heavy or ground calcium carbonate (II) is a surface-treated grade of heavy or ground calcium carbonate. 20. The curable composition according to claim 1, which contains 5 to 500 parts by weight of heavy or ground calcium carbonate (II) per 100 parts by weight of the vinyl polymer (I). 21. The curable composition according to claim 1, which comprises 0.1 to 20 parts by weight of a silane coupling agent as a (C) component. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
TECHNICAL FIELD OF THE INVENTION The present invention relates to a curable composition. More particularly, it relates to a curable composition which comprises a vinyl polymer having at least one crosslinking silyl group, together with heavy or ground calcium carbonate having a specific surface area of not smaller than 1.5 m.sup.2 /g but not larger than 50 m.sup.2 /g. BACKGROUND ART Unlike polymers obtained by ionic polymerization or polycondensation, few vinyl polymers obtainable by radical polymerization and having a functional group, in particular a terminal functional group, have been put to practical use. Among vinyl polymers, (meth)acrylic polymers have high weatherability, transparency and other characteristics that cannot be possessed by the polyether polymers, hydrocarbon polymers or polyester polymers. (Meth) acrylic polymers having an alkenyl group or crosslinking silyl group on their side chains are being utilized in high-weatherability coating compositions and the like. On the other hand, the polymerization of acrylic polymers is not easy to control because of side reactions. Moreover, introduction of functional group into terminus is very difficult. Vinyl polymers having an alkenyl group at a molecular chain terminus, if obtained by a simple and easy method, cured products excellent in cured product physical properties will possibly be obtained as compared with vinyl polymers having crosslinking groups on their side chains. Therefore, investigations concerning the methods of production thereof have been made by a number of researchers. However, it is not easy as yet to produce them on an industrial 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 group-terminated (meth) acrylic polymers which uses an alkenyl group-containing disulfide as a chain transfer agent. In Japanese Kokai Publication Hei-05-262808, there is disclosed a method of synthesizing alkenyl group-terminated (meth)acrylic polymers which comprises synthesizing a vinyl polymer having a hydroxyl group at both termini using a hydroxyl group-containing disulfide and further utilizing the reactivity of the hydroxyl group. In Japanese Kokai Publication Hei-05-211922, there is disclosed a method of synthesizing silyl group-terminated (meth)acrylic polymers which comprises synthesizing a vinyl polymer having a hydroxyl group at both termini using a hydroxyl group-containing polysulfide and further utilizing the reactivity of the hydroxyl group. By any of these methods, however, it is difficult to introduce functional groups into both termini of the molecule with certainty so that a cured product having satisfactory characteristics may hardly be obtained. For introducing functional groups into both termini of the molecule with certainty, it is essential to use a large amount of the chain transfer agent, and this is a problem from the production process viewpoint. In carrying out these methods, ordinary radical polymerization is used, so that it is difficult to control the molecular weight and molecular weight distribution (ratio between weight average molecular weight and number average molecular weight) of the polymer to be obtained. In view of such state of the art, the present inventors have so far made a large number of inventions relating to various crosslinking functional group-terminated vinyl polymers, methods of producing the same, curable compositions comprising the same and uses thereof (see, for example, 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). For example, a vinyl polymer having a silicon-containing group (hereinafter also referred to as "crosslinking silyl group"), which has a silicon atom-bound hydroxyl group or a hydrolyzable group and is capable of being crosslinked under formation of a siloxane bond, or cured products derived from a composition comprising such vinyl polymer are excellent in heat resistance and weatherability and are applicable in various uses, including, but being not limited to, sealants such as elastic sealants for building and construction and sealants for multilayer glass, materials for electric and electronic parts, such as solar battery backside sealants, electric insulating materials such as insulating sheath for electric wires and cables, pressure sensitive adhesives, adhesives, elastic adhesives, paints, powder coatings, coating materials, foamed articles, potting agents for electric and electronic use, films, gaskets, casting materials, various molding materials, and rustproof and waterproof sealants for end faces (cut edges)of net glass or laminated glass. Among them, elastic sealants for building and construction contain in many cases general-purpose heavy or ground calcium carbonate having a specific surface area of about 1 m.sup.2 /g as incorporated therein. This is for the purpose of reducing the cost of compositions and improving the restorability of cured products, among others. However, when such general-purpose heavy or ground calcium carbonate is used in the above-mentioned vinyl polymers having a crosslinking functional group, there arises a problem in that cured products showing a high level of elongation as required of elastic sealants for building and construction can hardly be obtained. Furthermore, the curable composition tends to readily string, hence improvements in viscosity ratio and knife releasability are required in certain instances. On the other hand, as a demand from the relevant market, not only sealants for multilayer glass but also elastic sealants for building and construction (in particular single-component elastic sealants) are required to be capable of firmly bonding to various adherends without applying any primer, namely to be excellent in non-primer adhesiveness. Furthermore, sealing compositions for use in contact with glass, for example sealants for multilayer glass, are required to be excellent in weather-resistant adhesiveness, in particular. However, when the above-mentioned general-purpose heavy or ground calcium carbonate is used in combination with the above-mentioned crosslinking functional group-containing vinyl polymers, the non-primer adhesiveness and weather-resistant adhesiveness are unsatisfactory. A particular problem is that the weather-resistant adhesiveness to highly insulating, heat ray-reflecting glass whose surface is coated with a metal oxide or the like is insufficient. DISCLOSURE OF THE INVENTION It is an object of the present invention to improve the viscosity ratio and knife releasability of a curable composition whose main component is a vinyl polymer having at least one crosslinking functional group and improve the cured products obtained therefrom with respect to their breaking strength, breaking elongation, adhesiveness to various adherends, and weather-resistant adhesiveness to various kinds of glass, in particular heat ray-reflecting glass. In view of the state of the art as explained above, the present inventors made intensive investigations and, as a result, found that when a specific filler is added to the above polymer, the viscosity ratio and knife releasability of the resulting composition can be improved without lowering the rate of curing of the composition or without otherwise adversely affecting the same and, at the same time, the breaking strength, breaking elongation, adhesiveness and weather-resistant adhesiveness of the cured products to various adherends derived therefrom can be improved. The inventors have thus solved the above-discussed problems and have been led to completion of the present invention. The invention thus provides a curable composition which comprises the following two components: a vinyl polymer (I) having at least one crosslinking functional group, and heavy or ground calcium carbonate (II) having a specific surface area of not smaller than 1.5 m.sup.2 /g but not larger than 50 m.sup.2 /g. The main chain of the vinyl polymer (I) is not particularly restricted but preferably is one produced by polymerizing a monomer selected from the group consisting of (meth)acrylic monomers, acrylonitrile monomers, aromatic vinyl monomers, fluorine-containing vinyl monomers and silicon-containing vinyl monomers as a main monomer, more preferably one produced by polymerizing a (meth) acrylic monomer, still more preferably an acrylic monomer, much more preferably an acrylic ester monomer, most preferably a butyl acrylate monomer. The ratio of the weight average molecular weight (Mw) and number average molecular weight (Mn), namely the ratio Mw/Mn, of the vinyl polymer (I) as determined by gel permeation chromatography is not particularly restricted but preferably is less than 1.8. The main chain of the vinyl polymer (I) is not particularly restricted but preferably is one produced by living radical polymerization, more preferably by atom transfer radical polymerization. The catalyst to be used in the atom transfer radical polymerization is not particularly restricted but preferably is a complex of a metal selected from the group consisting of copper, nickel, ruthenium and iron, more preferably a copper complex. The crosslinking functional group of the vinyl polymer (I) is not particularly restricted but preferably is a crosslinking silyl group, alkenyl group, hydroxyl group, amino group, polymerizable carbon-carbon double bond, or epoxy group, or the like. The position of the crosslinking functional group within the vinyl polymer (I) is not restricted but preferably is a terminal site. Although the polymer may additionally have a similar functional group within the main chain, it is desirable, when the crosslinked cured product is required to have rubber elasticity, for instance, that the polymer have a functional group only at a terminus. The number of crosslinking functional groups in the vinyl polymer (I) is not particularly restricted but, for obtaining cured products higher in crosslinking efficiency, it is, on the average, not less than 1, preferably not less than 1.2, more preferably not less than 1.5. The vinyl polymer (I) is not restricted but preferably is one produced by living radical polymerization, more preferably by atom transfer radical polymerization. Further, the atom transfer radical polymerization is not restricted but preferably is carried out using, as the catalyst, a complex elected from among transition metal complexes in which the main atom is an element of the group 7, 8, 9, 10 or 11 of the periodic table of the elements, more preferably a complex selected from the group consisting of complexes of copper, nickel, ruthenium, and iron, most preferably a copper complex. The heavy or ground calcium carbonate (II) having a specific surface area of not smaller than 1.5 m.sup.2 /g but not larger than 50 m.sup.2 /g is not particularly restricted but preferably is surface-treated heavy or ground calcium carbonate. The mixing proportion thereof is not particularly restricted, either. It is preferred, however, that the composition contain 5 to 500 parts by weight of the heavy or ground calcium carbonate (II) per 100 parts by weight of the vinyl polymer (I). For improving the adhesiveness, and the weather-resistant adhesiveness to glass, 0.1 to 20 parts by weight of a silane coupling agent is preferably used in combination as component (C), without any particular limitation. When the curable composition according to the invention, which comprises a vinyl polymer having a crosslinking functional group, is used, the viscosity ratio of the curable composition increases and the knife releasability is improved, and the mechanical properties and adhesiveness of the cured products obtained therefrom are improved. By using the curable composition of the invention, it becomes possible to obtain cured products high in elongation (e.g. EB) without causing decreases in strength (e.g. M50, Tmax). BEST MODES FOR CARRYING OUT THE INVENTION The present invention thus relates to a curable composition improved in the viscosity ratio and knife releasability thereof and in the breaking strength, breaking elongation, adhesiveness and weather-resistant adhesiveness to various adherends, of the cured products, which comprises a vinyl polymer (I) having at least one crosslinking functional group, and heavy or ground calcium carbonate (II) having a specific surface area of not smaller than 1.5 m.sup.2 /g but not larger than 50 m.sup.2 /g. In the following, the curable composition of the invention is described in detail. Re: Vinyl Polymer (I) Main Chain The vinyl monomer constituting the main chain of the vinyl polymer (I) according to the invention is not particularly restricted but includes various species. As examples, there may be mentioned (meth) acrylic monomers such as (meth) acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, toluyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, .gamma.-(methacryloyloxypropyl)trimethoxysilane, (meth)acrylic acid-ethylene oxide adducts, trifluoromethylmethyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethylmethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, and 2-perfluorohexadecylethyl (meth)acrylate; styrenic monomers such as styrene, vinyltoluene, .alpha.-methylstyrene, chlorostyrene, styrenesulfonic acid and salts thereof; fluorine-containing vinyl monomers such as perfluoroethylene, perfluoropropylene, and vinylidene fluoride; silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; maleic anhydride, maleic acid, and maleic acid monoalkyl esters and dialkyl esters; fumaric acid, and fumaric acid monoalkyl esters and dialkyl esters; maleimide monomers such as maleimide, methylmaleimide, ethylmaleimide, propylmaleimide, butylmaleimide, hexylmaleimide, octylmaleimide, dodecylmaleimide, stearylmaleimide, phenylmaleimide, and cyclohexylmaleimide; nitrile group-containing vinyl monomers such as acrylonitrile and methacrylonitrile; amide group-containing vinyl monomers such as acrylamide and methacrylamide; vinyl esters such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, and vinyl cinnamate; alkenes such as ethylene and propylene; conjugated dienes such as butadiene and isoprene; vinyl chloride, vinylidene chloride, allyl chloride, allyl alcohol, and the like. These may be used singly or a plurality of them may be subjected to copolymerization. Among them, styrenic monomers and (meth) acrylic monomers are preferred from the viewpoint of physical properties of products. Acrylic ester monomers and methacrylic ester monomers are more preferred, acrylic ester monomers are particularly preferred, and butyl acrylate is most preferred. In the practice of the invention, these preferred monomers maybe copolymerized or block copolymerized with other monomers. On such occasion, these preferred monomers preferably account for at least 40% by weight of the monomer composition. In the above form of expression, "(meth) acrylic acid", for instance, means acrylic acid and/or methacrylic acid. The molecular weight distribution, namely the ratio between the weight average molecular weight and number average molecular weight as determined by gel permeation chromatography, of the polymer (I) according to the invention is not particularly restricted but preferably is less than 1.8 but not less than 1.01, preferably not more than 1.7 but not less than 1.01, more preferably not more than 1.6 but not less than 1.01, still more preferably not more than 1.5 but not less than 1.01, particularly preferably not more than 1.4 but not less than 1.01, most preferably not more than 1.3 but not less than 1.01. In the practice of the invention, the GPC measurement is generally carried out on a polystyrene gel column using chloroform as a mobile phase, and the number average molecular weight can be determined on the polystyrene equivalent basis. The number average molecular weight of the vinyl polymer according to the invention is not particularly restricted but preferably within the range of 500 to 1,000,000, more preferably 1,000 to 100,000. Method of Main Chain Synthesis Although the method of synthesizing the vinyl polymer (I) according to the invention is not restricted, controlled radical polymerization is preferred, living radical polymerization is more preferred, and atom transfer radical polymerization is particularly preferred. These are explained in the following. Controlled Radical Polymerization Radical polymerization methods can be classified into "ordinary radical polymerization methods" which comprise merely copolymerizing a monomer having a specific functional group and a vinyl monomer using an azo compound, a peroxide or the like as a polymerization initiator, and "controlled radical polymerization methods" by which a specific functional group can be introduced into a controlled site, for example a terminus. "Ordinary radical polymerization methods" are simple and easy to perform but allow the specific functional group-containing monomer to be introduced into the polymer only at random. For obtaining polymers with a high percentage of functionalization, it is necessary to use this monomer in fairly large amounts. When, conversely, only a small amount of the monomer is used, the problem arises that the proportion of polymer molecules formed without introduction of this specific functional group increases. Further, since they consist in free radical polymerization, there is another problem, namely only polymers with a wide molecular weight distribution and a high viscosity can be obtained. "Controlled radical polymerization methods" can be further classified into "chain transfer agent methods" which comprise carrying out polymerization using a chain transfer agent having a specific functional group to give functional group-terminated vinyl polymers and "living radical polymerization methods" by which growing polymer termini can grow, without undergoing termination and like reactions, to give polymers with a molecular weight approximately as designed. "Chain transfer agent methods" can give polymers with a high level of functionalization but require the use of a fairly large amount of a chain transfer agent having a specific functional group relative to the initiator, hence have economical problems, inclusive of treatment-related problems. Like the above-mentioned "ordinary radical polymerization methods", there is also the problem that only polymers having a wide molecular weight distribution and a high viscosity can be obtained because of their consisting in free radical polymerization. Unlike these polymerization methods, "living radical polymerization methods" hardly undergo termination reactions and can give polymers with a narrow molecular weight distribution (Mw/Mn being about 1.1 to 1.5) and make it possible to arbitrarily control the molecular weight by changing the monomer-to-initiator formulating ratio, in spite of their belonging to the class of radical polymerization methods regarded as being difficult to control because of high rates of polymerization and a tendency toward ready occurrence of termination reactions, such as radical-to-radical coupling. Therefore, such "living radical polymerization methods" are more preferred as the methods of producing the specific functional group-containing vinyl polymers mentioned above, since they can give polymers narrow in molecular weight distribution and low in viscosity and, in addition, make it possible to introduce specific functional group-containing monomers into the polymers at almost arbitrary positions. The term "living polymerization", in its narrow sense, means a mode of polymerization in which molecular chains grow while their terminus always retain activity. In the ordinary sense, however, the term also includes the mode of pseudo-living polymerization in which molecular chains grow while terminally inactivated ones and terminally activated ones are in equilibrium. The latter definition applies also in the present invention. In recent years, "living radical polymerization methods" have actively been studied by a large number of groups of researchers. For example, there may be mentioned the one using a cobalt porphyrin complex, as described in the Journal of the American Chemical Society (J. Am. Chem. Soc.), 1994, vol. 116, page 7943, the one using a radical capping agent, such as a nitroxide compound, as described in Macromolecules, 1994, vol. 27, page 7228, and "atom transfer radical polymerization" (ATRP) using an organic halide or the like as an initiator and a transition metal complex as a catalyst. Among the "living radical polymerization methods", the "atom transfer radical polymerization", by which vinyl monomers are polymerized using an organic halide or halogenated sulfonyl compound, among others, as an initiator and a transition metal complex as a catalyst, are more preferred as the method of producing specific functional group-containing vinyl polymers, since it not only has the above characteristic features of "living radical polymerization" but also gives polymers having a terminal halogen atom relatively convenient for functional group conversion reactions and, further, the degree of freedom is large in initiator and catalyst designing. As examples of this atom transfer radical polymerization, there may be mentioned those described in Matyjaszewski et al.: J. Am. Chem. Soc., 1995, vol. 117, page 5614, Macromolecules, 1995, vol. 28, page 7901, Science, 1996, vol. 272, page 866, WO 96/30421, WO 97/18247, WO 98/01480, WO 98/40415 and Sawamoto et al.: Macromolecules, 1995, vol. 28, page 1721, Japanese Kokai Publication Hei-09-208616 and Japanese Kokai Publication Hei-08-41117, among others. Which of such living radical polymerization methods is to be used is not critical in the practice of the present invention. Preferred, however, is the atom transfer radical polymerization. In the following, this living radical polymerization is described in detail. Prior thereto, one mode of controlled radical polymerization, namely polymerization using a chain transfer agent, which can be used in producing the polymer (I) to be described later herein, is first described. The radical polymerization using a chain transfer agent (telomer) is not particularly restricted but includes, for example, the following two methods for producing vinyl polymers having a terminal structure suited for being utilized in the practice of the present invention. One method produces halogen-terminated polymers by using a halogenated hydrocarbon as a chain transfer agent, as described in Japanese Kokai Publication Hei-04-132706, and the other produces hydroxyl-terminated polymers using a hydroxyl-containing mercaptan or a hydroxyl-containing polysulfide or the like as a chain transfer agent, as described in Japanese Kokai Publication Sho-61-271306, JP 2594402 or Japanese Kokai Publication Sho-54-47782. The living radical polymerization is now described. First, the method which uses a radical capping agent such as a nitroxide compound is described. In this polymerization, a nitroxy free radial (.dbd.N--O.), which is generally stable, is used as a radical capping agent. Such compound includes, as preferred species, but is not limited to, 2,2,6,6-tetrasubstituted-1-piperidinyloxy radicals, 2,2,5,5-tetrasubstituted-1-pyrrolidinyloxy radicals and like cyclic hydroxyamine-derived nitroxy free radicals. Suitable as the substituent are alkyl groups containing not more than 4 carbon atoms, such as methyl or ethyl. Specific nitroxy free radical compounds include, but are not limited to, 2,2,6,6-tetramethyl-1-piperidinyloxy radical (TEMPO), 2,2,6,6-tetraethyl-1-piperidinyloxy radical, 2,2,6,6-tetramethyl-4-oxo-1-piperidinyloxy radical, 2,2,5,5-tetramethyl-1-pyrrolidinyloxy radical, 1,1,3,3-tetramethyl-2-isoindolinyloxy radical and N,N-di-t-butylamine-oxy radical. It is also possible to use other stable free radicals, such as galvinoxyl free radical, in lieu of nitroxy free radicals. The above radical capping agent is used in combination with a radical generator. Presumably, a reaction product formed from the radical capping agent and radical generator serves as a polymerization initiator to allow the polymerization of addition-polymerizable monomers to proceed. Although the ratio between both is not particularly restricted, the radical initiator is used appropriately in an amount of 0.1 to 10 moles per mole of the radical capping agent. While various compounds can be used as the radical generator, a peroxide capable of generating a radical under polymerization temperature conditions is preferred. Such peroxide includes, but is not limited to, diacyl peroxides such as benzoyl peroxide and lauroyl peroxide, dialkyl peroxides such as dicumyl peroxide and di-t-butyl peroxide, peroxycarbonates such as diisopropyl peroxydicarbonate and bis(4-t-butylcyclohexyl) peroxydicarbonate, and alkyl peresters such as t-butyl peroxyoctoate and t-butyl peroxybenzoate. In particular, benzoyl peroxide is preferred. Further, other radical generators, for example radical-generating azo compounds such as azobisisobutyronitrile can be used in lieu of peroxides. Alkoxyamine compounds such as those illustrated below may be used as initiators in lieu of the combined use of a radical capping agent and a radical generator, as reported in Macromolecules, 1995, vol. 28, page 2993. ##STR1## When an alkoxyamine compound is used as an initiator and that compound is one having a functional group, such as a hydroxyl group, such as the one illustrated above, functional group-terminated polymers are obtained. When this is utilized in the practice of the present invention, functional group-terminated polymers can be obtained. The polymerization conditions, including monomers, solvent and polymerization temperature, to be used in the above-mentioned polymerization using a radical capping agent such as a nitroxide compound are not particularly restricted but may be the same as those used in the atom transfer radical polymerization mentioned below. Atom Transfer Radical Polymerization Now, the atom transfer radical polymerization method, which is more preferred as the living radical polymerization in carrying out the present invention is described. In this atom transfer radical polymerization, an organic halide, in particular a highly reactive carbon-halogen bond-containing organic halide (e.g. a carbonyl compound having a halogen at an .alpha.-position or a compound having a halogen at a benzyl position), a halogenated sulfonyl compound or the like is used as an initiator. Specific examples are as follows: C.sub.6 H.sub.5 --CH.sub.2 X, C.sub.6 H.sub.5 --C(H) (X)CH.sub.3, C.sub.6 H.sub.5 --C(X) (CH.sub.3).sub.2 (in the above chemical formulas, C.sub.6 H.sub.5 is a phenyl group and X is a chlorine, bromine or iodine atom); R.sup.1 --C(H) (X)--CO.sub.2 R.sup.2, R.sup.1 --C(CH.sub.3) (X)--CO.sub.2 R.sup.2, R.sup.1 --C(H) (X)--C(O)R.sup.2, R.sup.1 --C(CH.sub.3) (X)--C(O)R.sup.2 (in the above formulas, R.sup.1 and R.sup.2 each is a hydrogen atom or an alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms and X is a chlorine, bromine or iodine atom); R.sup.1 --C.sub.6 H.sub.4 --SO.sub.2 X (in the above formula, R.sup.1 is a hydrogen atom or an alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms and X is a chlorine, bromine or iodine atom); and the like. An organic halide or a halogenated sulfonyl compound having a further functional group in addition to the functional group for initiating the polymerization may also be used as the initiator in atom transfer radical polymerization. In such case, vinyl polymers having the functional group at one main chain terminus and the structure of the growing terminus in atom transfer radical polymerization at the other main chain terminus are produced. As such functional group, there may be mentioned alkenyl, crosslinking silyl, hydroxyl, epoxy, amino and amide groups, among others. The alkenyl group-containing organic halide is not particularly restricted but includes, among others, those having a structure represented by the general formula 1: R.sup.4 R.sup.5 C(X)--R.sup.6 --R.sup.7 --C(R.sup.3).dbd.CH.sub.2 (1) (wherein R.sup.3 is a hydrogen atom or a methyl group, R.sup.4 and R.sup.5 each is a hydrogen atom or a univalent alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms and such R.sup.4 and R.sup.5 groups may be bonded together at the respective other ends , R.sup.6 is --C(O)O-- (ester group), --C(O)-- (keto group) or an o-, m- or p-phenylene group, R.sup.7 is a direct bond or a divalent organic group containing 1 to 20 carbon atoms, which may contain one or more ether bonds, and X is a chlorine, bromine or iodine atom.) As specific examples of the substituent R.sup.4 and R.sup.5, there may be mentioned a hydrogen atom, and methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl and like groups. R.sup.4 and R.sup.5 may be bonded together at the respective other ends to form a cyclic skeleton. As specific examples of the alkenyl-containing organic halide represented by the general formula 1, there may be mentioned the following: XCH.sub.2 C(O)O(CH.sub.2).sub.n CH.dbd.CH.sub.2, H.sub.3 CC(H) (X)C(O)O(CH.sub.2).sub.n CH.dbd.CH.sub.2, (H.sub.3 C).sub.2 C(X)C(O)O(CH.sub.2).sub.n CH.dbd.CH.sub.2, CH.sub.3 CH.sub.2 C(H) (X)C(O)O(CH.sub.2).sub.n CH.dbd.CH.sub.2, ##STR2## (in the above formulas, X is a chlorine, bromine or iodine atom and n is an integer of 0 to 20); XCH.sub.2 C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m CH.dbd.CH.sub.2, H.sub.3 CC(H) (X)C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m CH.dbd.CH.sub.2, (H.sub.3 C).sub.2 C(X)C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m CH.dbd.CH.sub.2, CH.sub.3 CH.sub.2 C(H) (X)C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m CH.dbd.CH.sub.2, ##STR3## (in the above formulas, X is a chlorine, bromine or iodine atom, n is an integer of 1 to 20 and m is an integer of 0 to 20); o-, m-, p-XCH.sub.2 --C.sub.6 H.sub.4 --(CH.sub.2).sub.n --CH.dbd.CH.sub.2, o-, m-, p-CH.sub.3 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.n --CH.dbd.CH.sub.2, o-, m-, p-CH.sub.3 CH.sub.2 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.n --CH.dbd.CH.sub.2 (in the above formulas, X is a chlorine, bromine or iodine atom and n is an integer of 0 to 20); o-, m-, p-XCH.sub.2 --C.sub.6 H.sub.4 --(CH.sub.2).sub.n --O--(CH.sub.2).sub.m --CH.dbd.CH.sub.2, o-, m-, p-CH.sub.3 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.n --O--(CH.sub.2).sub.m --CH.dbd.CH.sub.2, o-, m-, p-CH.sub.3 CH.sub.2 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.n --O--(CH.sub.2).sub.m --CH.dbd.CH.sub.2 (in the above formulas, X is a chlorine, bromine or iodine atom, n is an integer of 1 to 20 and m is an integer of 0 to 20); o-, m-, p-XCH.sub.2 --C.sub.6 H.sub.4 --O--(CH.sub.2).sub.n --CH.dbd.CH.sub.2, o-, m-, p-CH.sub.3 C(H) (X)--C.sub.6 H.sub.4 --O--(CH.sub.2).sub.n --CH.dbd.CH.sub.2, o-, m-, p-CH.sub.3 CH.sub.2 C(H) (X)--C.sub.6 H.sub.4 --O--(CH.sub.2).sub.n --CH.dbd.CH.sub.2 (in the above formulas, X is a chlorine, bromine or iodine atom and n is an integer of 0 to 20); o-, m-, p-XCH.sub.2 --C.sub.6 H.sub.4 --O--(CH.sub.2).sub.n --O--(CH.sub.2).sub.m --CH.dbd.CH.sub.2, o-, m-, p-CH.sub.3 C(H) (X)--C.sub.6 H.sub.4 --O--(CH.sub.2).sub.n --O--(CH.sub.2).sub.m --CH.dbd.CH.sub.2, o-, m-, p-CH.sub.3 CH.sub.2 C(H) (X)--C.sub.6 H.sub.4 --O--(CH.sub.2).sub.n --O--(CH.sub.2).sub.m --CH.dbd.CH.sub.2 (in the above formulas, X is a chlorine, bromine or iodine atom, n is an integer of 1 to 20 and m is an integer of 0 to 20). As the alkenyl-containing organic halide, there may further be mentioned compounds represented by the general formula 2: H.sub.2 C.dbd.C(R.sup.3)--R.sup.7 --C(R.sup.4) (X)--R.sup.8 --R.sup.5 (2) (wherein R.sup.3, R.sup.4, R.sup.5, R.sup.7 and X are as defined above and R.sup.8 represents a direct bond, --C(O)O-- (ester group), --C(O)-- (keto group) or an o-, m- or p-phenylene group). R.sup.6 is a direct bond or a divalent organic group (which may contain one or more ether bonds) containing 1 to 20 carbon atoms. When it is a direct bond, a vinyl group is bound to the carbon atom to which a halogen is bound, whereby an allyl halide compound is formed. In this case, the carbon-halogen bond is activated by the neighboring vinyl group, so that R.sup.8 is not always required to be a C(O)O or phenylene group, for instance, but may be a direct bond. When R.sup.7 is other than a direct bond, R.sup.8 should preferably be a C(O)O, C(O) or phenylene group so that the carbon-halogen bond may be activated. Specific examples of the compound of general formula 2 are as follows: CH.sub.2.dbd.CHCH.sub.2 X, CH.sub.2.dbd.C(CH.sub.3)CH.sub.2 X, CH.sub.2.dbd.CHC(H) (X)CH.sub.3, CH.sub.2.dbd.C(CH.sub.3)C(H) (X)CH.sub.3, CH.sub.2.dbd.CHC(X) (CH.sub.3).sub.2, CH.sub.2.dbd.CHC(H) (X)C.sub.2 H.sub.5, CH.sub.2.dbd.CHC(H) (X)CH(CH.sub.3).sub.2, CH.sub.2.dbd.CHC(H) (X)C.sub.6 H.sub.5, CH.sub.2.dbd.CHC(H) (X)CH.sub.2 C.sub.6 H.sub.5, CH.sub.2.dbd.CHCH.sub.2 C(H) (X)--CO.sub.2 R, CH.sub.2.dbd.CH(CH.sub.2).sub.2 C(H) (X)--CO.sub.2 R, CH.sub.2.dbd.CH(CH.sub.2).sub.3 C(H) (X)--CO.sub.2 R, CH.sub.2.dbd.CH(CH.sub.2).sub.8 C(H) (X)--CO.sub.2 R, CH.sub.2.dbd.CHCH.sub.2 C(H) (X)--C.sub.6 H.sub.5, CH.sub.2.dbd.CH(CH.sub.2).sub.2 C(H) (X)--C.sub.6 H.sub.5, CH.sub.2.dbd.CH(CH.sub.2).sub.3 C(H) (X)--C.sub.6 H.sub.5 (in the above formulas, X is a chlorine, bromine or iodine atom and R is an alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms), etc. The following may be mentioned as specific examples of the alkenyl-containing halogenated sulfonyl compound: o-, m-, p-CH.sub.2.dbd.CH--(CH.sub.2).sub.n --C.sub.6 H.sub.4 --SO.sub.2 X, o-, m-, p-CH.sub.2.dbd.CH--(CH.sub.2).sub.n --O--C.sub.6 H.sub.4 --SO.sub.2 X (in the above formulas, X is a chlorine, bromine or iodine atom and n is an integer of 0 to 20); etc. The above-mentioned crosslinking silyl-containing organic halide is not particularly restricted but includes, among others, compounds having a structure represented by the general formula 3: R.sup.4 R.sup.5 C(X)--R.sup.6 --R.sup.7 --C(H)(R.sup.3)--CH.sub.2 --[Si(R.sup.9).sub.2-b (Y).sub.b O].sub.m --Si(R.sup.10).sub.3-a (Y).sub.a (3) (wherein R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and X are as defined above, R.sup.9 and R.sup.10 each represents an alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms or a triorganosiloxy group represented by (R').sub.3 SiO-- (in which R' is a univalent hydrocarbon group containing 1 to 20 carbon atoms and the three R' groups may be the same or different) and, when there are two or more R.sup.9 or R.sup.10 groups, they may be the same or different; Y represents a hydroxyl group or a hydrolyzable group and, when there are two or more Y groups, they may be the same or different; a represents 0, 1, 2 or 3, b represents 0, 1 or 2, and m is an integer of 0 to 19 provided that the relation a+mb.gtoreq.1 is satisfied). Specific examples of the compound of general formula 3 are as follows: XCH.sub.2 C(O)O(CH.sub.2).sub.n Si(OCH.sub.3).sub.3, CH.sub.3 C(H) (X)C(O)O(CH.sub.2).sub.n Si(OCH.sub.3).sub.3, (CH.sub.3).sub.2 C(X)C(O)O(CH.sub.2).sub.n Si(OCH.sub.3).sub.3, XCH.sub.2 C(O)O(CH.sub.2).sub.n Si(CH.sub.3) (OCH.sub.3).sub.2, CH.sub.3 C(H) (X)C(O)O(CH.sub.2).sub.n Si(CH.sub.3) (OCH.sub.3).sub.2, (CH.sub.3).sub.2 C(X)C(O)O(CH.sub.2).sub.n Si(CH.sub.3) (OCH.sub.3).sub.2 (in the above formulas, X is a chlorine, bromine or iodine atom and n is an integer of 0 to 20); XCH.sub.2 C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m Si(OCH.sub.3).sub.3, H.sub.3 CC(H) (X)C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m Si(OCH.sub.3).sub.3, (H.sub.3 C).sub.2 C(X)C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m Si(OCH.sub.3).sub.3, CH.sub.3 CH.sub.2 C(H) (X)C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m Si(OCH.sub.3).sub.3, XCH.sub.2 C (O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m --Si(CH.sub.3) (OCH.sub.3).sub.2, H.sub.3 CC(H) (X)C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m --Si(CH.sub.3) (OCH.sub.3).sub.2, (H.sub.3 C).sub.2 C(X)C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m --Si(CH.sub.3) (OCH.sub.3).sub.2, CH.sub.3 CH.sub.2 C(H) (X)C(O)O(CH.sub.2).sub.n O(CH.sub.2).sub.m --Si(CH.sub.3) (OCH.sub.3).sub.2 (in the above formulas, X is a chlorine, bromine or iodine atom, n is an integer of 1 to 20 and m is an integer of 0 to 20); o-, m-, p-XCH.sub.2 --C.sub.6 H.sub.4 --(CH.sub.2).sub.2 Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.2 Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 CH.sub.2 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.2 Si(OCH.sub.3).sub.3, o-, m-, p-XCH.sub.2 --C.sub.6 H.sub.4 --(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 CH.sub.2 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, o-, m-, p-XCH.sub.2 --C.sub.6 H.sub.4 --(CH.sub.2).sub.2 --O--(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.2 --O--(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 CH.sub.2 C(H) (X)--C.sub.6 H.sub.4 --(CH.sub.2).sub.2 --O--(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, o-, m-, p-XCH.sub.2 --C.sub.6 H.sub.4 --O--(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 C(H) (X)--C.sub.6 H.sub.4 --O--(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 CH.sub.2 C(H) (X)--C.sub.6 H.sub.4 --O--(CH.sub.2).sub.3 --Si(OCH.sub.3).sub.3, o-, m-, p-XCH.sub.2 --C.sub.6 H.sub.4 --O--(CH.sub.2).sub.2 --O--(CH.sub.2).sub.3 --Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 C(H) (X)--C.sub.6 H.sub.4 --O--(CH.sub.2).sub.2 --O(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, o-, m-, p-CH.sub.3 CH.sub.2 C(H) (X)--C.sub.6 H.sub.4 --O--(CH.sub.2).sub.2 --O--(CH.sub.2).sub.3 Si (OCH.sub.3).sub.3 (in the above formulas, X is a chlorine, bromine or iodine atom); etc. As further examples of the above-mentioned crosslinking silyl-containing organic halide, there may be mentioned compounds having a structure represented by the general formula 4: (R.sup.10).sub.3-a (Y).sub.a Si--[OSi(R.sup.9).sub.2-b (Y).sub.b ].sub.m --CH.sub.2 --C(H)(R.sup.3)--R.sup.7 --C(R.sup.4) (X)--R.sup.8 --R.sup.5 (4) (wherein R.sup.3, R.sup.4, R.sup.5, R.sup.7, R.sup.8, R.sup.9, R.sup.10, a, b, m, X and Y are as defined above). Specific examples of such compound are as follows: (CH.sub.3 O).sub.3 SiCH.sub.2 CH.sub.2 C(H) (X)C.sub.6 H.sub.5, (CH.sub.3 O).sub.2 (CH.sub.3)SiCH.sub.2 CH.sub.2 C(H) (X)C.sub.6 H.sub.5, (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.2 C(H) (X)--CO.sub.2 R, (CH.sub.3 O).sub.2 (CH.sub.3)Si(CH.sub.2).sub.2 C(H) (X)--CO.sub.2 R, (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3 C(H) (X)--CO.sub.2 R, (CH.sub.3 O).sub.2 (CH.sub.3)Si(CH.sub.2).sub.3 C(H) (X)--CO.sub.2 R, (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.4 C(H) (X)--CO.sub.2 R, (CH.sub.3 O).sub.2 (CH.sub.3)Si(CH.sub.2).sub.4 C(H) (X)--CO.sub.2 R, (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.9 C(H) (X)--CO.sub.2 R, (CH.sub.3 O).sub.2 (CH.sub.3)Si(CH.sub.2).sub.9 C(H) (X)--CO.sub.2, (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.3 C(H) (X)--C.sub.6 H.sub.5, (CH.sub.3 O).sub.2 (CH.sub.3)Si(CH.sub.2).sub.3 C(H) (X)--C.sub.6 H.sub.5, (CH.sub.3 O).sub.3 Si(CH.sub.2).sub.4 C(H) (X)--C.sub.6 H.sub.5, (CH.sub.3 O).sub.2 (CH.sub.3)Si(CH.sub.2).sub.4 C(H) (X)--C.sub.6 H.sub.5 (in the above formulas, X is a chlorine, bromine or iodine atom and R is an alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms); etc. The above-mentioned hydroxyl-containing organic halide or halogenated sulfonyl compound is not particularly restricted but includes, for example, the following: HO--(CH.sub.2).sub.n --OC(O)C(H)(R)(X) (wherein X is a chlorine, bromine or iodine atom, R is a hydrogen atom or an alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms and n is an integer of 1 to 20). The above-mentioned amino group-containing organic halide or halogenated sulfonyl compound is not particularly restricted but includes, for example, the following: H.sub.2 N--(CH.sub.2).sub.n --OC(O)C(H)(R)(X) (wherein X is a chlorine, bromine or iodine atom, R is an alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms and n is an integer of 1 to 20). The above-mentioned epoxy-containing organic halide or halogenated sulfonyl compound is not particularly restricted but includes, for example, the following: ##STR4## (wherein X is a chlorine, bromine or iodine atom, R is a hydrogen atom or an alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms and n is an integer of 1 to 20). For obtaining a polymer having two or more terminal structures according to the present invention in each molecule, an organic halide or halogenated sulfonyl compound having two or more initiation sites is preferably used as the initiator. As specific examples, there may be mentioned the following: ##STR5## (in the above formulas, C.sub.6 H.sub.4 is a phenylene group and X is a chlorine, bromine or iodine atom); ##STR6## (in the above formulas, R is an alkyl, aryl or aralkyl group containing 1 to 20 carbon atoms, n is an integer of 0 to 20 and X is a chlorine, bromine or iodine atom); ##STR7## (in the above formulas, X is a chlorine, bromine or iodine atom and n is an integer of 0 to 20); ##STR8## (in the above formulas, n is an integer of 1 to 20 and X is a chlorine, bromine or iodine atom); ##STR9## (in the above formulas, X is a chlorine, bromine or iodine atom); etc. The vinyl monomers to be used in this polymerization are not particularly restricted but all those monomers mentioned hereinabove as examples can appropriately be used. The transition metal complex to be used as the catalyst is not particularly restricted but preferably is a metal complex containing, as the main metal, an element of the group 7, 8, 9, 10 or 11 of the periodic table. More preferred are complexes of zero-valent copper, univalent copper, divalent ruthenium, divalent iron or divalent nickel. Copper complexes are preferred among others. Specific examples of the univalent copper compound to be used are cuprous chloride, cuprous bromide, cuprous iodide, cuprous cyanide, cuprous oxide and cuprous perchlorate. When such a copper compound is used, a ligand such as 2,2'-bipyridyl or a derivative thereof, 1,10-phenanthroline or a derivative thereof or a polyamine such as tetramethylethylenediamine, pentamethyldiethylenetriamine or hexamethyltris(2-aminoethyl)amine is added for increasing the catalytic activity. The tristriphenylphosphine complex of divalent ruthenium chloride (RuCl.sub.2 (PPh.sub.3).sub.3) is also suited for use as the catalyst. When such a ruthenium compound is used as the catalyst, an aluminum alkoxide is added as an activator. Furthermore, the divalent iron-bistriphenylphosphine complex (FeCl.sub.2 (PPh.sub.3).sub.2), the divalent nickel-bistriphenylphosphine complex (NiCl.sub.2 (PPh.sub.3).sub.2), and the divalent nickel-bistributylphosphine complex (NiBr.sub.2 (PBu.sub.3).sub.2) are also suited for use as the catalyst. The polymerization can be carried out without using any solvent or in the presence of various solvents. As the solvent species, there may be mentioned hydrocarbon solvents such as benzene and toluene, ether solvents such as diethyl ether and tetrahydrofuran, halogenated hydrocarbon solvents such as methylene chloride and chloroform, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, alcohol solvents such as methanol, ethanol, propanol, isopropanol, n-butyl alcohol and tert-butyl alcohol, nitrile solvents such as acetonitrile, propionitrile and benzonitrile, ester solvents such as ethyl acetate and butyl acetate, carbonate solvents such as ethylene carbonate and propylene carbonate, and the like. These may be used singly or two or more of them may be used in admixture. The polymerization can be carried out within the temperature range of 0.degree. C. to 200.degree. C., preferably 50 to 150.degree. C., although it is not limited to such range. Functional Groups The crosslinking functional group in the vinyl polymer (I) is not restricted. Preferred as such are, however, crosslinking silyl, alkenyl, hydroxyl, amino, polymerizable carbon-carbon double bond, epoxy and like groups. These crosslinking functional groups all can be used so as to adapt to the intended use/purpose. Number of Crosslinking Functional Groups The number of crosslinking functional groups in the vinyl polymer (I) is not particularly restricted but, for obtaining cured products with higher crosslinkability, it should be, on an average, not less than 1, preferably not less than 1.2, more preferably not less than 1.5. Positions of Crosslinking Functional Groups In cases where the foamed products resulting from foaming and curing of the curable composition of the present invention are especially required to have rubber-like properties, it is preferred that at least one of crosslinking functional groups be positioned at a terminus of the molecular chain so that the molecular weight between crosslinking sites, which has a great influence on the rubber elasticity, can be increased. More preferably, all crosslinking groups are located at molecular chain termini. Methods of producing vinyl polymers, in particular (meth)acrylic polymers, having at least one crosslinking functional group such as mentioned above at a molecular terminus thereof are disclosed in Japanese Kokoku Publication Hei-03-14068, Japanese Kokoku Publication Hei-04-55444 and Japanese Kokai Publication Hei-06-211922, among others. However, these methods are free radical polymerization methods in which the above-mentioned "chain transfer agent methods" is used and, therefore, the polymers obtained generally have problems, namely they show a molecular weight distribution represented by Mw/Mn as wide as not less than 2 as well as a high viscosity, although they have crosslinking functional groups, in relatively high proportions, at molecular chain termini. Therefore, for obtaining vinyl polymers showing a narrow molecular weight distribution and a low viscosity and having crosslinking functional groups, in high proportions, at molecular chain termini, the above-described "living radical polymerization method" is preferably used. In the following, an explanation is made of these functional groups. Crosslinking Silyl Groups As the crosslinking silyl groups to be used in the practice of the present invention, there may be mentioned those groups represented by the general formula 5: --[Si(R.sup.9).sub.2-b (Y).sub.b O].sub.m --Si(R.sup.10).sub.3-a (Y).sub.a (5) {wherein, R.sup.9 and R.sup.10 each is 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 (R').sub.3 SiO-- (in which R' is a univalent hydrocarbon group containing 1 to 20 carbon atoms and the three R' groups may be the same or different) and, when there are two or more R.sup.9 or R.sup.10 groups, they may be the same or different; Y represents a hydroxyl group or a hydrolyzable group and, when there are two or more Y groups, they may be the same or different; a represents 0, 1, 2 or 3, b represents 0, 1 or 2, and m is an integer of 0 to 19, provided that the relation a+mb.gtoreq.1 should be satisfied.} As the hydrolyzable group, there may be mentioned, among others, a hydrogen atom and those groups which are in general use, for example alkoxy, acyloxy, ketoximate, amino, amido, aminoxy, mercapto and alkenyloxy groups. Among them, alkoxy, amido and aminoxy groups are preferred. In view of mild hydrolyzability and ease of handling, alkoxy groups are particularly preferred. One to three hydroxyl groups and/or hydrolyzable groups can be bound to each silicon atom and, in the practice of the present invention, it is preferred that (a+.SIGMA.b) be within the range of 1 to 5. When there are two or more hydrolyzable groups or hydroxyl groups in one crosslinking silyl group, they may be the same or different. The number of silicon atoms forming the crosslinking silyl group is not less than 1 and, in the case of silicon atoms connected by siloxane or like bonding, it is preferably not more than 20. Particularly preferred are crosslinking silyl groups represented by the general formula 6: --Si(R.sup.10).sub.3-a (Y).sub.a (6) (wherein R.sup.10, Y and a are as defined above) because of ready availability. Alkenyl Groups The alkenyl group to be used in the practice of the invention is not particularly restricted but preferably is one represented by the general formula 7: H.sub.2 C.dbd.C(R.sup.11)-- (7) (wherein R.sup.11 is a hydrogen atom or a hydrocarbon group containing 1 to 20 carbon atoms). In the general formula 7, R.sup.11 is a hydrogen atom or a hydrocarbon group containing 1 to 20 carbon atoms, typical examples of which are the following: --(CH.sub.2).sub.n --CH.sub.3, --CH(CH.sub.3)--(CH.sub.2).sub.n --CH.sub.3, --CH(CH.sub.2 CH.sub.3)--(CH.sub.2).sub.n --(CH.sub.3, --CH(CH.sub.2 CH.sub.3).sub.2, --C(CH.sub.3).sub.2 --(CH.sub.2).sub.n --CH.sub.3, --C(CH.sub.3) (CH.sub.2 CH.sub.3)--(CH.sub.2).sub.n --CH.sub.3, --C.sub.6 H.sub.5, --C.sub.6 H.sub.5 (CH.sub.3), --C.sub.6 H.sub.5 (CH.sub.3).sub.2, --(CH.sub.2).sub.n --C.sub.6 H.sub.5, --(CH.sub.2).sub.n --C.sub.6 H.sub.5 (CH.sub.3), --(CH.sub.2).sub.n --C.sub.6 H.sub.5 (CH.sub.3).sub.2 (n being an integer of not less than 0 and the total number of carbon atoms in each group being not more than 20). Among them, a hydrogen atom is preferred. It is preferred, though not obligatory, that the alkenyl group in the polymer (I) be not activated by a carbonyl or alkenyl group or an aromatic ring, which is conjugated with the carbon-carbon double bond of the alkenyl group. The mode of bonding of the alkenyl group to the polymer is not particularly restricted but preferably involves carbon-carbon bonding, ester bonding, carbonate bonding, amide bonding, urethane bonding or the like. Amino Groups In the practice of the invention, the amino group is not particularly restricted but includes groups represented by --NR.sup.12.sub.2 (wherein R.sup.12 is a hydrogen atom or an organic group containing 1 to 20 carbon atoms and the two R.sup.12 groups may be the same or different or may be bonded together at the respective other ends to form a ring structure). It may be an ammonium salt represented by --(NR.sup.12.sub.3).sup.+ X.sup.- (wherein R.sup.12 is as defined above and X.sup.- is a counter anion), without any problem. In the above formulas, R.sup.12 is a hydrogen atom or a univalent organic group containing 1 to 20 carbon atoms and includes, among others, a hydrogen atom, alkyl groups containing 1 to 20 carbon atoms, aryl groups containing 6 to 20 carbon atoms, and aralkyl groups containing 7 to 20 carbon atoms. The two R.sup.12 groups may be the same or different, or may be bonded together at the respective other ends to form a ring structure. Polymerizable Carbon-carbon Double Bond The groups containing polymerizable carbon-carbon double bond are preferably groups represented by the general formula 8: --OC(O)C(R.sup.13).dbd.CH.sub.2 (8) (wherein R.sup.13 represents a hydrogen atom or a univalent organic group containing 1 to 20 carbon atoms), more preferably a group of formula (8) in which R.sup.13 is a hydrogen atom or a methyl group. Specific examples of R.sup.13 in general formula 8 include, but are not particularly limited to, --H, --CH.sub.3, --CH.sub.2 CH.sub.3, --(CH.sub.2).sub.n CH.sub.3 (n being an integer of 2 to 19), --C.sub.6 H.sub.5, --CH.sub.2 OH, --CN and the like. Preferred are --H and --CH.sub.3, however. Functional Group Introduction Method In the following, several methods of functional group introduction into the vinyl polymer (I) of the present invention are described without any purpose of restriction. First, methods of crosslinking silyl, alkenyl or hydroxyl group introduction by terminal functional group conversion are described. These functional groups each can serve as a precursor of another and, therefore, mention is made in the order from crosslinking silyl groups to respective precursors. As methods of synthesizing vinyl polymers having at least one crosslinking silyl group, there may be mentioned, among others, (A) the method which comprises subjecting a crosslinking silyl group-containing hydrosilane compound to addition to a vinyl polymer having at least one alkenyl group in the presence of a hydrosilylation catalyst, (B) the method which comprises reacting a vinyl polymer having at least one hydroxyl group with a compound having, in each molecule, a crosslinking silyl group and a group capable of reacting with the hydroxyl group, such as an isocyanato group, (C) the method which comprises subjecting a compound having, in each molecule, a polymerizable alkenyl group and a crosslinking silyl group to reaction in synthesizing a vinyl polymer by radical polymerization, (D) the method which comprises using a crosslinking silyl group-containing chain transfer agent in synthesizing a vinyl polymer by radical polymerization, and (E) the method which comprises reacting a vinyl polymer having at least one highly reactive carbon-halogen bond with a compound having, in each molecule, a crosslinking silyl group and a stable carbanion. The vinyl polymer having at least one alkenyl group, which is to be used in the above method (A), can be obtained by various methods. Several methods of synthesis are mentioned below, without any purpose of restriction, however. (A-a) Method comprising subjecting to reaction a compound having, in each molecule, a polymerizable alkenyl group together with a low polymerizability alkenyl group, such as one represented by the general formula 9 shown below as a second monomer in synthesizing a vinyl polymer by radical polymerization: H.sub.2 C.dbd.C(R.sup.14)--R.sup.15 --R.sup.16 --C(R.sup.17).dbd.CH.sub.2 (9) (wherein R.sup.14 represents a hydrogen atom or a methyl group, R.sup.15 represents --C(O)O-- or an o-, m- or p-phenylene group, R.sup.16 represents a direct bond or a divalent organic group containing 1 to 20 carbon atoms, which may contain one or more ether bonds, and R.sup.17 represents a hydrogen atom, an alkyl group containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon atoms or an aralkyl group containing 7 to 20 carbon atoms). The time when the compound having, in each molecule, a polymerizable alkenyl group together with a low polymerizability alkenyl group is subjected to reaction is not particularly restricted but, in particular in living radical polymerization and when rubber-like properties are expected, the compound is preferably subjected to reaction as a second monomer at the final stage of the polymerization reaction or after completion of the reaction of the employed monomers. (A-b) Method comprising subjecting to reaction a compound having at least two low polymerizability alkenyl groups, for example 1,5-hexadiene, 1,7-octadiene or 1,9-decadiene, at the final stage of the polymerization or after completion of the reaction of the monomers employed in vinyl polymer synthesis by living radical polymerization. (A-c) Method comprising reacting a vinyl polymer having at least one highly reactive carbon-halogen bond with one of various alkenyl-containing organometallic compounds, for example an organotin such as allyltributyltin or allyltrioctyltin, for substitution of the halogen. (A-d) Method comprising reacting a vinyl polymer having at least one highly reactive carbon-halogen bond with a stabilized, alkenyl-containing carbanion such as one represented by the general formula 10, for substitution of the halogen: M.sup.+ C.sup.- (R.sup.18) (R.sup.19)--R.sup.20 --C(R.sup.17).dbd.CH.sub.2 (10) (wherein R.sup.17 is as defined above, R.sup.18 and R.sup.19 each is an electron-withdrawing group capable of stabilizing the carbanion C.sup.- or one of them is such an electron-withdrawing group and the other represents a hydrogen atom, an alkyl group containing 1 to 10 carbon atoms or a phenyl group, R.sup.20 represents a direct bond or a divalent organic group containing 1 to 10 carbon atoms, which may contain one or more ether bonds, and M.sup.+ represents an alkali metal ion or a quaternary ammonium ion). Particularly preferred as the electron-withdrawing group R.sup.18 and/or R.sup.19 are those which have a structure of --CO.sub.2 R, --C(O)R or --CN. (A-e) Method comprising reacting a vinyl polymer having at least one highly reactive carbon-halogen bond with a simple substance metal, such as zinc, or an organometallic compound and then reacting the thus-prepared enolate anion with an alkenyl-containing, electrophilic compound, such as an alkenyl-containing compound having a leaving group such as a halogen atom or an acetyl group, an alkenyl-containing carbonyl compound, an alkenyl-containing isocyanate compound or an alkenyl-containing acid halide. (A-f) Method comprising reacting a vinyl polymer having at least one highly reactive carbon-halogen bond with an alkenyl-containing oxy anion or carboxylate anion such as one represented by the general formula (11) or (12), for substitution of the halogen: H.sub.2 C.dbd.C(R.sup.17)--R.sup.21 --O.sup.- M.sup.+ (11) (wherein R.sup.17 and M.sup.+ are as defined above |
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