Method for manufacturing natural rubber

1. A method for manufacturing natural rubber comprising:

adding to a natural rubber latex at least one sulfonic acid selected from the group consisting of dodecyl sulfonic acid, dodecyl benzenesulfonic acid, and polyoxyethylene lauryl ether sulfate; and, thereafter, drying and removing moisture from the mixture of the natural rubber latex and the sulfonic acid by spraying the natural rubber latex mixture into an atmosphere of shock waves generated by pulse combustion, removing magnesium present in the natural rubber latex, wherein the treatment for removing the magnesium in the natural rubber latex comprises adding a water soluble compound, which produces a magnesium salt that has poor solubility in water with the magnesium, to the natural rubber latex, the water soluble compound being selected from the group consisting of oxalic acid, oxalic acid salts, carbonate, boric acid, boric acid metal salt, metal hydroxide, and phosphoric acid; wherein the oxalic acid salt, the carbonate, the boric acid metal salt, and the metal hydroxide do not comprise magnesium.

2. The method for manufacturing natural rubber according to claim 1 , wherein the mixture of the natural rubber latex and the sulfonic acid is stirred at a temperature of from 0 to 100° C. for from 1 minute to 24 hours.

3. The method for manufacturing natural rubber according to claim 1 , wherein from 0.1 to 5.0 parts by weight of the sulfonic acid is added per 100 parts by weight of a solid component of the natural rubber latex.

4. The method for manufacturing natural rubber according to claim 1 , wherein the treatment for removing magnesium present in the natural rubber latex is performed prior to adding the sulfonic acid.

5. The method for manufacturing natural rubber according to claim 1 , wherein adding to a natural rubber latex at least one type of sulfonic acid further comprises diluting the sulfonic acid with water prior to adding, and wherein adding to a natural rubber latex at least one type of sulfonic acid comprises gradually adding the sulfonic acid to the natural latex rubber while thoroughly mixing.

6. The method for manufacturing natural rubber according to claim 1 , wherein from 0.1 to 3.0 parts by weight of the sulfonic acid is added per 100 parts by weight of a solid component of the natural rubber latex, and wherein the mixture of the natural rubber latex and the sulfonic acid is stirred at a temperature of from room temperature to 80° C. for from 5 minutes to 20 hours.

7. The method for manufacturing natural rubber according to claim 1 , wherein the moisture is removed by spraying the natural rubber latex mixture into an atmosphere of shock waves generated by pulse combustion at a frequency of from 50 to 1,200 Hz in a drying chamber having a temperature of from 40 to 100° C.

8. The method for manufacturing natural rubber according to claim 1 , wherein a Mooney viscosity at 125° C. of the natural rubber taken in accordance with Japanese Industry Standard (JIS) K6300 (MS1+4) is from 25 to 65.

9. The method for manufacturing natural rubber according to claim 1 , wherein the treatment for removing magnesium present in the natural rubber latex is performed prior to adding the sulfonic acid, the treatment including reducing an amount of magnesium in the natural rubber latex to 100 ppm or less per an amount of a solid component in the natural rubber latex.

10. The method for manufacturing natural rubber according to claim 1 , wherein the sulfonic acid is selected from the group consisting of dodecyl benzenesulfonic acid and polyoxyethylene lauryl ether sulfate.