Synthetic rubber latex and method for manufacturing same

1. A latex of a synthetic rubber, wherein a content rate of a particle having a particle size of 5 μm or more in a particle size distribution of a synthetic rubber particle comprised in the latex, as determined on a number basis, is less than 3,000 ppm by weight.

2. The latex of a synthetic rubber according to claim 1 , wherein the synthetic rubber corresponds to synthetic polyisoprene and/or a styrene-isoprene-styrene block copolymer.

3. A latex composition comprising the latex of a synthetic rubber according to claim 1 , and a vulcanizing agent and/or a vulcanization accelerator.

4. A film molded article comprising the latex composition according to claim 3 .

5. An adhesive layer formation substrate comprising an adhesive layer formed by use of the latex of a synthetic rubber according to claim 1 , on a substrate.

6. A method for producing a latex of a synthetic rubber, comprising:

a first step of mixing a polymer solution or a polymer dispersion liquid of a synthetic rubber, obtained by dissolution or dispersion of the synthetic rubber in an organic solvent, with an aqueous surfactant solution or a surfactant dispersion liquid obtained by dissolution or dispersion of a surfactant in water, to thereby obtain a mixture;

a second step of subjecting the mixture to a first dispersion treatment in a rotor/stator emulsifying machine, to thereby obtain a coarsely-dispersed emulsified liquid; and

a third step of subjecting the coarsely-dispersed emulsified liquid to a second dispersion treatment in a rotor/stator emulsifying machine, to thereby obtain a finely-dispersed emulsified liquid;

wherein when a dispersion energy F determined according to the following expressions (1) and (2) is defined as follows: a dispersion energy F applied to the mixture in the first dispersion treatment in the second step is defined as a first dispersion energy F 1 , a dispersion energy F applied to the coarsely-dispersed emulsified liquid in the second dispersion treatment in the third step is defined as a second dispersion energy F 2 , and a sum of the first dispersion energy F 1 and the second dispersion energy F 2 is defined as a total dispersion energy F total ,

the first dispersion treatment and the second dispersion treatment are performed such that the first dispersion energy F 1 is 8.0×10 7 or more and the total dispersion energy F total is 1.0×10 8 or more:

F 1 =( V 1 ×N 1 ×P 1 ×S 1 )/ Q 1 2   (1)

wherein V 1 represents a circumferential speed (m/s) of a rotor in the first dispersion treatment, N 1 represents a synthesis frequency (Hz) of the emulsifying machine in the first dispersion treatment, P 1 represents a volume (m 3 ) of an emulsification chamber in the first dispersion treatment, S 1 represents a cross-sectional area (m 2 ) of each slit provided on a rotor and a stator in the first dispersion treatment, and Q 1 represents a dispersion treatment speed (m 3 /s) in the first dispersion treatment,

F 2 =( V 2 ×N 2 ×P 2 ×S 2 )/ Q 2 2   (2)

wherein V 2 represents a circumferential speed (m/s) of a rotor in the second dispersion treatment, N 2 represents a synthesis frequency (Hz) of the emulsifying machine in the second dispersion treatment, P 2 represents a volume (m 3 ) of an emulsification chamber in the second dispersion treatment, S 2 represents a cross-sectional area (m 2 ) of each slit provided on a rotor and a stator in the second dispersion treatment, and Q 2 represents a dispersion treatment speed (m 3 /s) in the second dispersion treatment.

7. The method for producing a latex of a synthetic rubber according to claim 6 , wherein the second dispersion energy F 2 is 2.0×10 7 or more.