A cup lump natural rubber devoid of impurities with a size of greater than 0.5 mm and having a plasticity retention index of greater than 80 is provided. The use of such a natural rubber in a line for manufacturing a semi-finished product based on natural rubber makes it possible to ensure an improved compromise of performances which are the productivity of a line for manufacturing semi-finished products and the quality of the semi-finished products resulting from this production line.

A latex including: a nitrile rubber containing an α,β-ethylenically unsaturated nitrile monomer unit in a content of 8 to 50 wt % and an α,β-ethylenically unsaturated dicarboxylic acid monoester monomer unit in a content of 1 to 10 wt %, and having an iodine value of 120 g/100 g or less; and a benzisothiazoline-based compound represented by the following general formula (1), wherein the content of the benzisothiazoline-based compound is 50 ppm by weight or more, with respect to the nitrile rubber, and a redox potential of the latex is 80 to 800 mV. ##STR00001##
In the general formula (1) mentioned above, R.sup.1 represents a hydrogen atom, or a substituted or unsubstituted organic group, R.sup.2 each independently represents a hydrogen atom, or a substituted or unsubstituted organic group, and “n” represents an integer of 0 to 4.

A latex processing system and method involves mixing a latex and at least one solvent blend in an extruder, in order to remove resin found in the latex and to coagulate the latex to form a coagulum. The at least one solvent blend has a first solvent configured to coagulate the latex, and a second solvent configured to swell the resulting coagulum. In particular, a series of the solvent blends may be used at different locations along a length of the extruder, and may further include distinct blends of the first solvent and the second solvent, introduced at the different locations, and having different ratios of the first solvent and the second solvent.

A latex processing system and method involves mixing a latex and at least one solvent blend in an extruder, in order to remove resin found in the latex and to coagulate the latex to form a coagulum. The at least one solvent blend has a first solvent configured to coagulate the latex, and a second solvent configured to swell the resulting coagulum. In particular, a series of the solvent blends may be used at different locations along a length of the extruder, and may further include distinct blends of the first solvent and the second solvent, introduced at the different locations, and having different ratios of the first solvent and the second solvent.

A carboxyl group-containing nitrile rubber having an iodine value of 120 or less, wherein the content of sodium is 1500 ppm by weight or less, the total content of calcium, magnesium, and aluminum is 350 ppm by weight or less, and the storage elastic modulus at 140° C. is 350 kPa or more.

A carboxyl group-containing nitrile rubber comprising an α,β-ethylenically unsaturated nitrile monomer unit in a content of 5 to 60 wt % and having an iodine value of 120 or less, wherein the carboxyl group-containing nitrile rubber has a polymer Mooney viscosity (ML1+4, 100° C.) of 60 or less and a polymer pH of 7 or less.

A carboxyl group-containing nitrile rubber comprising an α,β-ethylenically unsaturated nitrile monomer unit in a content of 5 to 60 wt % and having an iodine value of 120 or less, wherein the carboxyl group-containing nitrile rubber has a polymer Mooney viscosity (ML1+4, 100° C.) of 60 or less and a polymer pH of 7 or less.

Provided herein are organic solvent-based processes for the removal of rubber from non-Hevea plants such as guayule shrubs. By the use of the processes, solid purified rubber can be obtained that contains 0.05-0.5 weight % dirt, 0.2-1.5 weight % ash, and 0.1-4 weight % resin (when it has been dried so as to contain 0.8 weight % volatile matter).

Provided herein are organic solvent-based processes for the removal of rubber from non-Hevea plants such as guayule shrubs. By the use of the processes, solid purified rubber can be obtained that contains 0.05-0.5 weight % dirt, 0.2-1.5 weight % ash, and 0.1-4 weight % resin (when it has been dried so as to contain 0.8 weight % volatile matter).

The present invention relates to a process for obtaining aging-resistant natural rubber, to a rubber composition comprising the thus-obtained natural rubber and to the use of this composition for producing consumer goods.