Carboxylic acid-modified nitrile-based copolymer latex, method for preparing same, latex composition for dip molding containing same, and dip-molded article
The present invention relates to a carbonic acid-modified nitrile-based copolymer latex, a process for producing the same, a latex composition for dip-molding comprising the latex composition and a molded article produced therefrom. More specifically, modified nitrile-based copolymer latex, which can improve the stability of latex even with the use of inorganic pigments by making the inherently modified nitrile-based copolymer latex, enables the production of a dip-molded article having a smoothness of syneresis, less stickiness, and excellent tensile strength, a process for producing the same, a latex composition for dip-molding comprising the same, and a molded article made therefrom.
1. A carbonic acid-modified nitrile-based copolymer latex which is produced adding starch during copolymerization and has a glass transition temperature of −50 to −15° C. and an average particle diameter of 50 to 500 nm, wherein the starch has a weight-average molecular weight of 300 to 30,000 g/mol.
2. The latex of claim 1 , wherein the starch is added in an amount of 1 to 30 parts by weight based on 100 parts by weight of the total amount of the monomers.
3. The latex of claim 1 , wherein the starch includes one selected from the group consisting of rice starch, barley starch, corn starch, waxy corn starch, tapioca starch, potato starch, sweet potato starch, wheat starch and modified starch thereof.
4. The latex of claim 3 , wherein the modified starch includes one selected from the group consisting of oxidized starch, acid-treated starch, ester starch, ether starch, phosphoric acid bridged starch, acetyl adipate acid starch, and combinations thereof.
5. The latex of claim 1 , wherein the carbonic acid-modified nitrile-based copolymer is by copolymerization of monomers comprising 40 to 89% by weight of a conjugated diene monomer, 10 to 50% by weight of an ethylenically unsaturated nitrile-based monomer and 0.1 to 10% by weight of an ethylenically unsaturated acid monomer.
6. The latex of claim 5 , wherein the conjugated diene monomer includes one selected from the group consisting of 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, isoprene, and combinations thereof.
7. The latex of claim 5 , wherein the ethylenically unsaturated nitrile-based monomer includes one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, α-chloronitrile, α-cyanoethyl acrylonitrile, and combinations thereof.
8. The latex of claim 5 , wherein the ethylenically unsaturated acid monomer includes one selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, maleic anhydride, citraconic anhydride, styrene sulfonic acid, monobutyl fumarate, monobutyl maleate, mono-2-hydroxypropyl maleate, and combinations thereof.
9. The latex of claim 1 , wherein the carbonic acid-modified nitrile-based copolymer latex is by copolymerization in which 0.3 to 30 parts by weight of an emulsifier, 0.01 to 2 parts by weight of a polymerization initiator and 0.1 to 2.0 parts by weight of a molecular weight modifier are added, based on 100 parts by weight of the total amount of monomers.
10. A latex composition for dip-molding comprising the carbonic acid-modified nitrile-based copolymer latex according to claim 1 .
11. A method of preparing a dip-molded article, said method comprising:
a) coating the surface of a mold with a coagulant solution;
b) coating the coagulant-coated mold with a latex composition for dip-molding to form a dip-molded layer;
c) cross-linking the dip-molded layer; and
d) peeling off the cross-linked dip-molded layer from the mold to obtain a dip-molded article,
wherein the latex composition for dip-molding is a latex composition for dip-molding according to claim 10 .