Surface treatment agent

1. A water- and oil-repellent agent which is an aqueous emulsion comprising:

(A) a fluorine-free polymer having a repeating unit derived from a fluorine-free (meth)acrylate ester monomer,

(B) a wax having a melting point of 52 to 88° C.,

(C) an aqueous medium, and

(D) an emulsifier,

wherein the fluorine-free (meth)acrylate ester monomer is a compound of the formula:

CH 2 ═CA 11 -C(═O)—O-A 12

wherein A 11 is a hydrogen atom or a methyl group, and

A 12 is a linear or branched hydrocarbon group having 18-30 carbon atoms,

the emulsifier comprises a sorbitan ester and another emulsifier, and the emulsifier has a hydrophilic-lipophilic balance (HLB) of 7.5 to 13.5,

wherein the another emulsifier is one polyether compound or a mixture of at least two polyether compounds, or is a polyether compound having a polyoxyalkylene group.

2. The water- and oil-repellent agent according to claim 1 , wherein A 11 is a hydrogen atom.

3. The water- and oil-repellent agent according to claim 1 , wherein the fluorine-free polymer further has a repeating unit derived from a halogenated olefin.

4. The water- and oil-repellent agent according to claim 1 , wherein the wax has a needle penetration of 15 or less.

5. The water- and oil-repellent agent according to claim 1 , wherein the wax is a paraffin wax.

6. The water- and oil-repellent agent according to claim 1 , wherein the another emulsifier is one polyether compound or a mixture of at least two polyether compounds.

7. The water- and oil-repellent agent according to claim 1 , wherein the another emulsifier is a polyether compound having a polyoxyalkylene group.

8. The water- and oil-repellent agent according to claim 7 , wherein the polyether compound is at least one selected from:

a compound represented by the formula:

R 11 O—(CH 2 CH 2 O) p —(R 12 O) q —R 13

wherein R 11 is an alkyl group having 1-22 carbon atoms, or an alkenyl group or an acyl group having 2-22 carbon atoms,

R 12 each is independently, the same or different, an alkylene group having at least 3 carbon atoms,

R 13 is a hydrogen atom, an alkyl group having 1-22 carbon atoms, or an alkenyl group having 2-22 carbon atoms,

p is a number of at least 2, and

q is a number of 0 or at least 1, and

an ester of an alcohol having 3 to 30 carbon atoms with a fatty acid having 5 to 30 carbon atoms, or

an alkylene oxide adduct of said ester.

9. The water- and oil-repellent agent according to claim 1 , wherein the hydrophilic-lipophilic balance (HLB) of the emulsifier is 8 to 12.

10. The water- and oil-repellent agent according to claim 1 , wherein a weight ratio of the fluorine-free polymer to the wax is 30/70 to 95/5.

11. The water- and oil-repellent agent according to claim 1 , wherein the amount of the fluorine-free polymer is 0.1 to 50% by weight, based on the water- and oil-repellent agent, the amount of the wax is 1 to 200 parts by weight, based on 100 parts by weight of the fluorine-free polymer, the amount of the emulsifier is 0.05 to 20 parts by weight, based on 100 parts by weight of total of the fluorine-free polymer or the wax, and the amount of the aqueous medium is 30 to 99% by weight, based on the water- and oil-repellent agent.

12. The water- and oil-repellent agent according to claim 1 , wherein the water- and oil-repellent agent does not contain a fluorine-containing polymer.

13. A method of producing the water- and oil-repellent agent according to claim 1 , comprising the steps of:

(i) polymerizing a monomer comprising a fluorine-free (meth)acrylate ester monomer in the presence of an emulsifier for polymer and an aqueous medium, to obtain an aqueous dispersion of a fluorine-free polymer having a repeating unit derived from the fluorine-free (meth)acrylate ester monomer,

(ii) dispersing a wax in water in the presence of an emulsifier for wax to obtain an aqueous dispersion of the wax, and

(iii) mixing the aqueous dispersion of the fluorine-free polymer with the aqueous dispersion of the wax.

14. The method according to claim 13 , wherein the hydrophilic-lipophilic balance of the emulsifier for polymer is 8 to 14, and the hydrophilic-lipophilic balance of the emulsifier for wax is 7 to 13.5.

15. A method of producing a treated substrate, comprising applying the water- and oil-repellent agent according to claim 1 to a substrate.