An electrophotographic photosensitive member includes: a conductive support; a charge generation layer disposed on the conductive support, the charge generation layer including a charge generating material and a vinyl copolymer, the vinyl copolymer including a structural unit including a chlorine atom, a structural unit including an acyloxy group, and a structural unit including an aromatic polycarboxylic acid structure, a proportion of the structural unit including a chlorine atom to all the structural units being 80% by mass or more, a proportion of the structural unit including an aromatic polycarboxylic acid structure to all the structural units being 0.5% by mass or more; and a charge transport layer disposed on the charge generation layer, the charge transport layer including a charge transporting material and a binder resin.

The present invention relates to a method for preparing a vinyl chloride-based polymer, including: bulk polymerizing a vinyl chloride-based monomer in a polymerization reactor to prepare a vinyl chloride-based polymer; and adding water and vapor to the polymerization reactor, and heating to remove an unreacted vinyl chloride-based monomer, wherein an addition amount of the water is 0.500 to 5.000 parts by weight based on 100 parts by weight of the vinyl chloride-based polymer.

The present invention relates to a method for preparing a vinyl chloride-based polymer, including: bulk polymerizing a vinyl chloride-based monomer in a polymerization reactor to prepare a vinyl chloride-based polymer; and adding water and vapor to the polymerization reactor, and heating to remove an unreacted vinyl chloride-based monomer, wherein an addition amount of the water is 0.500 to 5.000 parts by weight based on 100 parts by weight of the vinyl chloride-based polymer.

The present invention relates to a plasticizer composition, a resin composition, and a method of preparing the plasticizer composition. The plasticizer composition comprising an isophthalate-based material; and an epoxy-based alkyl ester compound represented by Chemical Formula 1. ##STR00001##

The present invention relates to a plasticizer composition, a resin composition, and a method of preparing the plasticizer composition. The plasticizer composition comprising an isophthalate-based material; and an epoxy-based alkyl ester compound represented by Chemical Formula 1. ##STR00001##

The present disclosure relates to a method for preparing a polyolefin using a supported hybrid metallocene catalyst. According to the present disclosure, a polyolefin having a narrow molecular weight distribution can be prepared very effectively by introducing a cocatalyst in an optimum content in the presence of a supported hybrid metallocene catalyst containing two or more metallocene compounds having a specific chemical structure. The polyolefin prepared according to the present disclosure exhibits excellent uniformity in chlorine distribution in polyolefin during chlorination, thereby significantly improving elongation of the chlorinated polyolefin, compatibility with PVC and impact reinforcing performance. Thus, it exhibits excellent chemical resistance, weather resistance, flame retardancy, processability and impact strength reinforcing effect, and can be suitably applied as an impact reinforcing agent for PVC pipes and window profiles.

The present disclosure relates to a method for preparing a polyolefin using a supported hybrid metallocene catalyst. According to the present disclosure, a polyolefin having a narrow molecular weight distribution can be prepared very effectively by introducing a cocatalyst in an optimum content in the presence of a supported hybrid metallocene catalyst containing two or more metallocene compounds having a specific chemical structure. The polyolefin prepared according to the present disclosure exhibits excellent uniformity in chlorine distribution in polyolefin during chlorination, thereby significantly improving elongation of the chlorinated polyolefin, compatibility with PVC and impact reinforcing performance. Thus, it exhibits excellent chemical resistance, weather resistance, flame retardancy, processability and impact strength reinforcing effect, and can be suitably applied as an impact reinforcing agent for PVC pipes and window profiles.

The present disclosure relates to a method for preparing a polyolefin using a supported hybrid metallocene catalyst. According to the present disclosure, a polyolefin having a narrow molecular weight distribution can be prepared very effectively by introducing a cocatalyst in an optimum content in the presence of a supported hybrid metallocene catalyst containing two or more metallocene compounds having a specific chemical structure. The polyolefin prepared according to the present disclosure exhibits excellent uniformity in chlorine distribution in polyolefin during chlorination, thereby significantly improving elongation of the chlorinated polyolefin, compatibility with PVC and impact reinforcing performance. Thus, it exhibits excellent chemical resistance, weather resistance, flame retardancy, processability and impact strength reinforcing effect, and can be suitably applied as an impact reinforcing agent for PVC pipes and window profiles.

Provided is a surface-treated calcium carbonate that can make a vinyl chloride-based resin composition less colorable in a weathering test and excellent in impact strength. The surface-treated calcium carbonate is a calcium carbonate subjected to treatment with a surface treatment agent in which a proportion of saturated fatty acid contained in a fatty acid is 85% by mass or more, and has a content of elemental iron of 0.01% by mass or less, a content of elemental zinc of 0.1 to 2% by mass introduced by the treatment with the surface treatment agent, and a BET specific surface area of 5 to 30 m.sup.2/g.

Provided is a surface-treated calcium carbonate that can make a vinyl chloride-based resin composition less colorable in a weathering test and excellent in impact strength. The surface-treated calcium carbonate is a calcium carbonate subjected to treatment with a surface treatment agent in which a proportion of saturated fatty acid contained in a fatty acid is 85% by mass or more, and has a content of elemental iron of 0.01% by mass or less, a content of elemental zinc of 0.1 to 2% by mass introduced by the treatment with the surface treatment agent, and a BET specific surface area of 5 to 30 m.sup.2/g.