Water-based surface treatment agent

A surface treatment agent which is an aqueous emulsion comprising:

• (1) a fluorine-free polymer consisting essentially of repeating units derived from:
• (a) a long-chain (meth)acrylate ester monomer represented by the formula:
• CH2═CA11-C(═O)—O-A12, wherein
• A11 is a hydrogen atom or a methyl group, and
• A12 is a linear or branched aliphatic hydrocarbon group having 10-30 carbon atoms;
• (c) a fluorine-free crosslinkable monomer that is a compound which has at least two olefinic carbon-carbon double bonds, at least two reactive groups, or at least one olefinic carbon-carbon double bond and at least one reactive group in which the reactive group is selected from the group consisting of a hydroxyl group, an epoxy group, a chloromethyl group, a blocked isocyanate group, an amino group, and a carboxyl group, and optionally
• (d) a halogenated olefin monomer,
• wherein the amount of the long-chain (meth)acrylate ester monomer (a) is at least 40% by weight, based on the polymer, and the amount of the fluorine-free crosslinkable monomer (c) is 0.5-20 parts by weight, and the amount of the halogenated olefin monomer (d) is 0-100 parts by weight, based on 100 parts by weight of the long-chain (meth)acrylate ester monomer (a),
• (2) a surface active agent comprising both of a nonionic surface active agent and an anionic surface active agent,
• wherein the nonionic surface active agent is selected from the group consisting of ethers, esters, ester ethers, alkanolamides, polyhydric alcohols and amine oxides, the amount of the surface active agent is from 1 to 20 parts by weight, based on 100 parts by weight of the polymer, and the amount of the anionic surface active agent is at least 15% by weight and at most 70% by weight, based on the total of the nonionic surface active agent and the anionic surface active agent;
• and
• (3) a liquid medium comprising water.