Abstract: A novel transition metal compound represented by the formula ##STR1## (wherein each of A.sup.1, A.sup.2, A.sup.3 and A.sup.4 is a cyclopentadienyl group, an indenyl group, a fluorenyl group or their derivative; A.sup.5 is a hydrocarbondiylidene group having 4 to 30 carbon atoms; a pair of A.sup.1 and A.sup.2 as well as a pair of A.sup.3 and A.sup.4 is respectively bonded to the identical carbon atom in A.sup.5 to form a crosslinking structure; each of R.sup.1 and R.sup.2 is a halogen atom, a hydrogen atom, an alkyl group or a silicon-containing alkyl group having 1 to 10 carbon atoms, an aryl group, an alkylaryl group, an arylalkyl group or a halogenated aryl group having 6 to 20 carbon atoms; R.sup.1 and R.sup.2 may be identical or different; each of M.sup.1 and M.sup.2 is titanium, zirconium or hafnium; and M.sup.1 and M.sup.2 may be mutually identical or different), and a method for polymerizing an olefin in the presence of this compound and a co-catalyst.

Abstract: A method for preparing a propylene (co)polymer having a substantially high syndiotactic structure and a desired molecular weight which comprises the step of (co)polymerizing propylene or propylene and a small amount of another olefin by the use of a transition metal compound catalyst having asymmetric ligands in the presence of a specific internal olefin.

Abstract: A transition metal compound represented by the formula ##STR1## (wherein each of A.sup.1, A.sup.2, A.sup.3 and A.sup.4 is a cyclopentadienyl group, an indenyl group, a fluorenyl group or their derivative; A.sup.5 is a hydrocarbondiylidene group having 4 to 30 carbon atoms; a pair of A.sup.1 and A.sup.2 as well as a pair of A.sup.3 and A.sup.4 is respectively bonded to the identical carbon atom in A.sup.5 to form a crosslinking structure; each of R.sup.1 and R.sup.2 is a halogen atom, a hydrogen atom, an alkyl group or a silicon-containing alkyl group having 1 to 10 carbon atoms, an aryl group, an alkylaryl group, an arylalkyl group or a halogenated aryl group having 6 to 20 carbon atoms; R.sup.1 and R.sup.2 may be identical or different; each of M.sup.1 and M.sup.2 is titanium, zirconium or hafnium; and M.sup.1 and M.sup.2 may be mutually identical or different), and a method for polymerizing an olefin in the presence of this compound and a co-catalyst.

Abstract: Aromatic polyamide having good high-temperature resistance and processing ability is obtained by specifying the ratio of storage modulus at the glass transition temperature (Tg).degree.C. to that of (Tg+100).degree.C.

Abstract: A polyamide and/or polyimide is prepared by using N,N'-dimethylethyleneurea or N,N'-dimethylpropyleneurea as a solvent upon polycondensation of a polycarboxylic acid and a diisocyanate at a temperature above 100.degree. C. in the presence of an alkali metal carbonate, alkali metal hydrogencarbonate, alkali metal hydroxide or an alkali metal salt of a polycarboxylic acid.

Abstract: Disclosed herein is a process for preparing heat-resistant polymers by reacting an organic polyisocyanate with one or more compounds selected from the group consisting of organic polycarboxylic acids and organic polycarboxylic acid anhydrides in the presence of an alkali metal fluoride or an alkali metal fluoride combined with a quaternary onium salt as a catalyst.

Abstract: Heat resistant organic fibers comprising a wholly aromatic polymer having amide group and/or imide group, said fibers having properties satisfying the following formulasTm.gtoreq.350.degree. C.,Tm-Tex.gtoreq.30.degree. C.Xc.gtoreq.10%DE.gtoreq.10%DSR(Tm).ltoreq.15%, and ##EQU1## wherein Tm is a melting point; Tex is an exotherm starting temperature; Xc is a degree or crystallization; DE is an elongation; DSR is a dry shrinkage factor at Tm; and DSR(Tm+55.degree. C.) is a dry shrinkage factor at Tm+55.degree. C. The process for producing the fibers is also disclosed.

Abstract: Disclosed herein is a process for preparing heat-resistant polymers by reacting an organic polyisocyanate with one or more compounds selected from the group consisting of organic polycarboxylic acids and organic polycarboxylic acid anhydrides in the presence of an alkali metal fluoride or an alkali metal fluoride combined with a quaternary onium salt as a catalyst.

Abstract: Disclosed is a catalyst for polymerizing .alpha.-olefins which comprises(A) a composition obtained by co-comminuting(a) a magnesium halide,(b) an organic acid ester,(c) a halogenated aliphatic or alicyclic hydrocarbon,(d) at least one ingredient selected from the group consisting of aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated aromatic hydrocarbons, liquid propylene oligomers and aromatic ethers, and(e) an aluminum halide optionally added thereto and then heat-treating the resulting mixture together with titanium tetrachloride;(B) an organic aluminum compound; and(C) an organic acid ester or a complex thereof with an aluminum halide.