An object of the present invention is to provide a curable composition having sufficient polymerization properties even under acidic conditions. The curable composition of the present invention includes (a) a polymerizable monomer having an acidic group, (b) a transition metal compound, (c) at least one compound selected from benzoxazole compounds and benzothiazole compounds, and (d) a reducing agent.

A solid catalyst component for the polymerization of olefins CH.sub.2═CHR, wherein R is hydrogen or a hydrocarbon radical with 1-12 carbon atoms, made from or containing Mg, Ti, Bi, a halogen and an electron donor.

A solid catalyst component for the polymerization of olefins CH.sub.2═CHR, wherein R is hydrogen or a hydrocarbon radical with 1-12 carbon atoms, made from or containing Mg, Ti, Bi, a halogen and an electron donor.

A Brønsted-Lowry acid initiator system for cationic polymerization of an ethylenically unsaturated monomer involves an initiator having a structure of Formula (I) in an anhydrous polymerization medium:

##STR00001## where: M is tantalum (Ta), vanadium (V) or niobium (Ni); R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and are independently H, F, Cl, Br, I, alkyl or aryl, or two or more of R.sub.2, R.sub.3, R.sub.4 and R.sub.5 on a same benzene ring are taken together to form a bicyclic, tricyclic or tetracyclic moiety with the benzene ring, with the proviso that all of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 on the same benzene ring are not H; L is absent or a molecule that coordinates to H.sup.+; and, x is 0 when L is absent, or x is 0.5 or more when L is present.

A Brønsted-Lowry acid initiator system for cationic polymerization of an ethylenically unsaturated monomer involves an initiator having a structure of Formula (I) in an anhydrous polymerization medium:

##STR00001## where: M is tantalum (Ta), vanadium (V) or niobium (Ni); R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and are independently H, F, Cl, Br, I, alkyl or aryl, or two or more of R.sub.2, R.sub.3, R.sub.4 and R.sub.5 on a same benzene ring are taken together to form a bicyclic, tricyclic or tetracyclic moiety with the benzene ring, with the proviso that all of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 on the same benzene ring are not H; L is absent or a molecule that coordinates to H.sup.+; and, x is 0 when L is absent, or x is 0.5 or more when L is present.

A Brønsted-Lowry acid initiator system for cationic polymerization of an ethylenically unsaturated monomer involves an initiator having a structure of Formula (I) in an anhydrous polymerization medium:

##STR00001## where: M is tantalum (Ta), vanadium (V) or niobium (Ni); R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and are independently H, F, Cl, Br, I, alkyl or aryl, or two or more of R.sub.2, R.sub.3, R.sub.4 and R.sub.5 on a same benzene ring are taken together to form a bicyclic, tricyclic or tetracyclic moiety with the benzene ring, with the proviso that all of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 on the same benzene ring are not H; L is absent or a molecule that coordinates to H.sup.+; and, x is 0 when L is absent, or x is 0.5 or more when L is present.

An object of the present invention is to provide a curable composition having sufficient polymerization properties even under acidic conditions. The curable composition of the present invention includes (a) a polymerizable monomer having an acidic group, (b) a transition metal compound, (c) at least one compound selected from benzoxazole compounds and benzothiazole compounds, and (d) a reducing agent.

A catalyst for the homopolymerization or copolymerization of CH.sub.2CHR olefins, made from or containing the product obtained by contacting: (i) a solid catalyst component made from or containing Ti, Mg, Cl, and an internal electron donor compound, wherein the solid catalyst component contains from about 0.1 to about 50 wt % of Bi, based upon the total weight of the solid catalyst component; (ii) an alkyl aluminum compound and, (iii) an external electron donor compound having the formula:
(R1)aSi(OR2)b
wherein R.sup.1 and R.sup.2 are independently selected from the group consisting of alkyl radicals with 1-8 carbon atoms and a is 0 or 1 and a+b=4.

A catalyst for the homopolymerization or copolymerization of CH.sub.2CHR olefins, made from or containing the product obtained by contacting: (i) a solid catalyst component made from or containing Ti, Mg, Cl, and an internal electron donor compound, wherein the solid catalyst component contains from about 0.1 to about 50 wt % of Bi, based upon the total weight of the solid catalyst component; (ii) an alkyl aluminum compound and, (iii) an external electron donor compound having the formula:
(R1)aSi(OR2)b
wherein R.sup.1 and R.sup.2 are independently selected from the group consisting of alkyl radicals with 1-8 carbon atoms and a is 0 or 1 and a+b=4.

A BrnstedLowry acid initiator system for cationic polymerization of an ethylenically unsaturated monomer involves an initiator having a structure of Formula (I) in an anhydrous polymerization medium (I) where: M is tantalum (Ta), vanadium (V) or niobium (Ni); each R.sub.1 is independently H, OR.sub.6, F, Cl, Br, I or alkyl, where R.sub.6 is H or alkyl; R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are independently H, F, Cl Br, I, alkyl or aryl, or two or more of R.sub.2, R.sub.3, R.sub.4 and R.sub.5 on a same benzene ring form a bicyclic, tricyclic or tetracyclic moiety with the benzene ring, with the proviso that all of R.sub.2, R.sub.3, R.sub.4 and R.sub.5 on the same benzene ring are not H; L is absent or a molecule that coordinates to H.sup.+; and, x is 0 when L is absent, or x is 0.5 or more when L is present.

##STR00001##