Prepreg and carbon fiber-reinforced composite material

A prepreg comprising:

• sizing agent-coated carbon fiber bundles coated with a sizing agent;
• and
• a thermosetting resin composition impregnated into the sizing agent-coated carbon fiber bundles,
• wherein
• the sizing agent includes an aliphatic epoxy compound (A) and an aromatic compound (B) at least containing an aromatic epoxy compound (B1),
• the aliphatic epoxy compound (A) and the aromatic epoxy compound (B1) are contained in a mass ratio of 52/48 to 80/20,
• the aliphatic epoxy compound (A) comprises a glycidyl ether epoxy compound obtained by reaction of epichlorohydrin with a polyol selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, polybutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and arabitol,
• the sizing agent has an epoxy equivalent of 350 to 550 g/eq,
• the sizing agent-coated carbon fiber bundles have an (a)/(b) ratio of 0.50 to 0.90, where (a) is a height (cps) of a component at a binding energy (284.6 eV) assigned to CHx, C—C, and C═C and (b) is a height (cps) of a component at a binding energy (286.1 eV) assigned to C—O in a C1s core spectrum of a surface of the sizing agent applied onto the carbon fiber bundles analyzed by X-ray photoelectron spectroscopy using AlKα1,2 as an X-ray source at a photoelectron takeoff angle of 15°,
• the thermosetting resin composition is an epoxy resin composition at least containing
• an epoxy resin (D11) of Formula (3) below and
• an epoxy resin (D12) of Formula (4) below, and
• the epoxy resin composition contains the epoxy resin (D11) in an amount of 25 to 50% by mass and the epoxy resin (D12) in an amount of 40 to 80% by mass relative to 100% by mass of the total epoxy resins contained,
• the thermosetting resin composition includes a latent hardener which is an aromatic amine hardener (E2) that is used in combination with the sizing agent, and if the sizing agent and the aromatic amine hardener (E2) are mixed in an amine equivalent/epoxy equivalent ratio of 0.9 to form a first mixture, and the first mixture is stored in an atmosphere of 25° C. and 60% RH for 20 days, then the glass transition point of the first mixture will increase by 25° C. or less,
• wherein the epoxy resin (D11) has a structure of Formula (3):
• wherein in Formula (3),
• each of R8 and R9 is at least one selected from the group consisting of C1-4 aliphatic hydrocarbon groups, C3-6 alicyclic hydrocarbon groups, C6-10 aromatic hydrocarbon groups, halogen atoms, acyl groups, a trifluoromethyl group, and a nitro group;
• n is an integer of 0 to 4;
• m is an integer of 0 to 5;
• when a plurality of R8s or R9s exist, R8s and R9s are each optionally the same or different;
• and
• Z is one selected from —O—, —S—, —CO—, —C(═O)O—, —SO2—, and —C(═O)NH—);
• and
• wherein the epoxy resin (D12) has a structure of Formula (4):
• wherein in Formula (4),
• R10 to R13 are at least one selected from the group consisting of a hydrogen atom, C1-4 aliphatic hydrocarbon groups, alicyclic hydrocarbon groups having a carbon number of 4 or less, and halogen atoms;
• and
• Y is one selected from —CH2—, —O—, —S—, —CO—, —C(═O)O—, —SO2—, and —C(═O)NH—.