Water dispersion, carbon fiber bundle, and unidirectional material

An aqueous dispersion in which a resin component is dispersed in water and which is used for bundling carbon fibers, the carbon fibers being used in production of a unidirectional material in which the carbon fibers oriented in one direction are impregnated with a resin, wherein:

• the resin component includes
• a first resin component that is an ethylene/α-olefin copolymer (A) satisfying all of requirements (a1) to (a3) below or an acid-modified product (B) of the ethylene/α-olefin copolymer (A):
• (a1) a kinematic viscosity at 100° C. is 10 mm2/s or more and 5,000 mm2/s or less,
• (a2) a content ratio of a constitutional unit derived from ethylene is 30 mol % or more and 85 mol % or less, and
• (a3) a molecular weight distribution (Mw/Mn) measured by gel permeation chromatography (GPC) and obtained in terms of polystyrene is 2.5 or less, and
• a second resin component that is at least one resin selected from the group consisting of an acrylic resin (C), a urethane-based resin (D), and diene-based rubber (E);
• and
• a proportion of a total mass of the resin component with respect to a total mass of the aqueous dispersion is 0.01% by mass or more and 50% by mass or less.

A carbon fiber bundle in which carbon fibers are bundled, the carbon fibers being used in production of a unidirectional material in which the carbon fibers oriented in one direction are impregnated with a resin, wherein:

• the carbon fibers are bundled by a bundling agent adhered to the carbon fibers;
• the bundling agent includes an ethylene/α-olefin copolymer (A) satisfying all of requirements (a1) to (a3) below or an acid-modified product (B) of the ethylene/α-olefin copolymer (A):
• (a1) a kinematic viscosity at 100° C. is 10 mm2/s or more and 5,000 mm2/s or less,
• (a2) a content ratio of a constitutional unit derived from ethylene is 30 mol % or more and 85 mol % or less, and
• (a3) a molecular weight distribution (Mw/Mn) of a molecular weight measured by gel permeation chromatography (GPC) and obtained in terms of polystyrene is 2.5 or less;
• and
• a storage elastic modulus of a resin component of the bundling agent at 25° C. is 100 MPa or more and 100,000 MPa or less, the bundling agent including the ethylene/α-olefin copolymer (A) or the acid-modified product (B) thereof.

A carbon fiber bundle in which carbon fibers are bundled, the carbon fibers being used in production of a unidirectional material in which the carbon fibers oriented in one direction are impregnated with a resin, wherein:

• the carbon fibers are bundled by a bundling agent adhered to the carbon fibers;
• and
• the bundling agent includes
• a first resin component that is an ethylene/α-olefin copolymer (A) satisfying all of requirements (a1) to (a3) below or an acid-modified product (B) of the ethylene/α-olefin copolymer (A):
• (a1) a kinematic viscosity at 100° C. is 10 mm2/s or more and 5,000 mm2/s or less,
• (a2) a content ratio of a constitutional unit derived from ethylene is 30 mol % or more and 85 mol % or less, and
• (a3) a molecular weight distribution (Mw/Mn) of a molecular weight measured by gel permeation chromatography (GPC) and obtained in terms of polystyrene is 2.5 or less, and
• a second resin component that is at least one resin selected from the group consisting of an acrylic resin (C), a urethane-based resin (D), and diene-based rubber (E).