KR20020039855A - Method for preparing latex having superior stability - Google Patents

Abstract

PURPOSE: Provided is a process for producing a rubber latex excellent in stability, the rubber latex can produce an acrylonitrile-butadiene-styrene resin excellent in high impact property and high transparency. CONSTITUTION: The process contains the step of emulsion-polymerizing 100pts.wt. of conjugated diene compound monomers and 0.01-3.0pts.wt. of a reactive emulsifier, wherein the conjugated diene compound is at least one selected from the group consisting of 1,3-butadiene, isoprene, and chloroprene, and the reactive emulsifier is at least one selected from the group consisting of an anionic emulsifier having an allyl group of a sulfate salt of polyoxyethylene allyl glycidic nonyl phenyl ether, a neutral emulsifier having a polyoxyethylene allyl glycidyl nonyl phenyl ether-based allyl group, an anionic emulsifier having a (meth)acryloyl group, and etc.

Description

Manufacturing method of rubber latex with excellent stability {METHOD FOR PREPARING LATEX HAVING SUPERIOR STABILITY}

[Industrial use]

The present invention relates to a method for producing a rubber latex having excellent stability, and more particularly to a method for producing a rubber latex having excellent stability using a reactive emulsifier in the production of the rubber latex.

[Prior art]

In the preparation of transparent acrylonitrile-butadiene-styrene (ABS) resins, the transparency is determined by the particle size and particle distribution of the rubbery polymer dispersed when the refractive index is properly controlled, and the coagulation produced in the subsequent process. It is greatly affected by water.

In order to obtain an acrylonitrile-butadiene-styrene resin having excellent impact resistance and transparency, a large diameter rubber latex is required. As a conventional method for preparing the same, the following methods are known.

Iii) preparing small-diameter rubber latex, adding inorganic acids such as acetic acid, phosphoric acid, or organic acidic substances such as polymer flocculant to lower pH and fusion particles to produce large-diameter rubber latex;

Ii) a method for producing large-diameter particles by freezing small-diameter rubber latex;

Iii) a method for preparing a large diameter rubber latex by adding an acrylate copolymer latex or adding a polyvalent metal electrolyte during the polymerization;

Iii) a method for producing large diameter rubber latex by applying shear force to small diameter rubber latex;

Iii) a small amount of acrylonitrile monomer introduced into the comonomer

Iii) A method for producing large diameter rubber latex by appropriately adjusting the amount of emulsifier and the ionic strength.

The method of iii) to iii) has the advantage that it is possible to manufacture large diameter rubber latex within a short time, but there is a problem that a lot of coagulum is produced and the reproducibility of polymerization is insufficient and it is difficult to control to an appropriate size. Therefore, a device for filtering the coagulum and a process are required, but a problem arises in that an unwanted coagulum produced during the process is added, which causes a significant decrease in transparency. In addition, the method of iii) has a problem in that unreacted monomers have to be removed after rubber latex polymerization, and in particular, transparency is lower than that of pure diene rubber latex at low temperature impact strength. In addition, the method of iii) requires a long reaction time and a low concentration of the emulsifier, so that a large amount of coagulum is generated and it is difficult to remove the reaction heat during stirring.

In view of the problems of the prior art, it is an object of the present invention to provide a method for producing a rubber latex having excellent stability.

Another object of the present invention is to increase the stability, to reduce the formation of coagulum, to produce a rubber latex having a narrow rubber particle size distribution, as well as to prepare a transparent acrylonitrile-butadiene-styrene resin having excellent high impact and high transparency. It is to provide a rubber latex with excellent stability.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a rubber latex manufacturing method excellent in stability,

Iii) conjugated diene compound monomer

Ii) adding a reactive emulsifier to provide a method for producing a rubber latex having excellent stability including the step of emulsion polymerization.

Hereinafter, the present invention will be described in detail.

[Action]

The present invention increases the stability by adding a reactive emulsifier to the conjugated diene compound monomer to increase the stability to reduce the formation of coagulum, and to prepare a rubber latex with a narrow rubber particle size distribution, as well as high impact and high transparency It is to prepare a rubber latex having excellent stability capable of producing acrylonitrile-butadiene-styrene resin.

The present invention for this purpose, the rubber latex is

Iii) 100 parts by weight of the conjugated diene compound monomer;

Ii) 0.01 to 3.0 parts by weight of a reactive emulsifier is added to polymerize by emulsion polymerization.

More specifically,

a) in the reactor

Iii) 50 to 100 parts by weight of the conjugated diene compound monomer;

Ii) 0.5 parts by weight or less of a reactive emulsifier;

V) 1 to 4 parts by weight of a non-reactive emulsifier;

Iii) 0.2 to 1.5 parts by weight of a polymerization initiator;

V) 0.5 to 2 parts by weight of electrolyte;

Iii) 0.1 to 0.5 parts by weight of a molecular weight modifier; And

Viii) 75 to 100 parts by weight of ion-exchanged water

Dosing in a batch to react at 65 to 75 ° C. for 4 to 15 hours;

b) reactants of step a)

V) 50 parts by weight or less of the remaining conjugated diene compound monomers; And

Iii) 0.1 to 0.5 parts by weight of molecular weight regulator

To batch or continuous dosing and reacted at 70 to 85 ° C. for 10 to 20 hours.

step; And

c) the polymerization conversion rate of the reactant of step b) is 30-70% of the total compound

Ii) 0.01 to 3.0 parts by weight of a reactive emulsifier

Steps to apply

It is preferable to be prepared by a method comprising a.

(Iii) The conjugated diene compound monomers are reacted by collectively administering 50 to 100 parts by weight of the total conjugated diene compound monomers before the start of polymerization, and then the remaining conjugated diene compound monomers are collectively administered or continuously administered.

Iii) The conjugated diene compound monomers may be used alone or in combination with aromatic vinyl compounds such as styrene and α-methylstyrene, and vinyl cyan compounds such as acrylonitrile, and 15 parts by weight of the total monomer mixture. It is preferable to use within.

(Iii) The conjugated diene compound may be selected from one or more selected from the group consisting of 1,3-butadiene, isoprene, chloroprene, and pyreriden.

The ii) reactive emulsifier used in the rubber latex manufacturing method of the present invention may be an anionic emulsifier having an allyl group, a (meth) acryloyl group, and a propenyl group, or a neutral emulsifier.

Anionic emulsifiers having an allyl group may include sulfate salts of polyoxyethylene allylglycidyl nonylphenyl ether. Examples of useful anionic emulsifiers include ADEKARIA SOAP SE series (manufactured by Asahi Denka), and neutral allyl groups. Systemic emulsifiers include polyoxyethylene allylglycidyl nonylphenyl ether series, and useful ones on the market include the ADEKARIA SOAP NE series (product of Asahi Denka). The anionic emulsifier having a (meth) acryloyl group is useful in the market as the ELEMINOL RS series (manufactured by Sanyo Kasei), and the neutral emulsifier is the RMA-560 series (manufactured by Nippon Surfactant). Anionic emulsifiers having a propene group include ammonium sulfate salts of polyoxyethylene allylglycidyl nonyl propenyl phenyl ether, and useful in the market include AQUARON HS series, and neutral emulsifiers include AQUARON BC ( Daiichi Kogyo Seyaku's products) series. These reactive emulsifiers may be used alone or as a mixture of two or more thereof, and may be used by mixing with a non-reactive emulsifier.

In addition, the ii) reactive emulsifier is preferably added 0.01 to 3.0 parts by weight during the emulsion polymerization, it is preferable to use less than 3.0. If it is 3.0 or more, the mother liquor of latex may not be isolate | separated well in the aggregation process after acrylonitrile butadiene-styrene polymerization, and aggregation may be low.

(Iii) The non-reacting emulsifier may be selected from one or more selected from the group consisting of alkyl aryl sulfonates, alkali methyl alkyl sulfates, sulfonated alkyl esters, fatty acid soaps, and alkali salts of rosin acid.

In the production method of the present invention, a rubber latex can be prepared by adding a molecular weight regulator and a polymerization initiator used in conventional emulsion polymerization.

Specifically, the iii) polymerization initiator is a water-soluble persulfate of sodium persulfate, or potassium persulfate; Fat-soluble polymerization initiators of cumenehydro peroxide, diisopropyl benzene hydroperoxide, azobis isobutylonitrile, tertiary butyl hydroperoxide, paramethane hydroperoxide, or benzoyl peroxide; And an oxidation-reduction type polymerization initiator can be used by selecting at least one type.

And iii) KCl, NaCl, KHCO ₃ , NaHCO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , KHSO ₃ , NaHSO ₃ , K ₄ P ₂ O ₇ , Na ₄ P ₂ O ₇ , K ₃ PO ₄ , At least one selected from the group consisting of Na ₃ PO ₄ , Na ₂ HPO ₄ , and Na ₂ HPO ₄ can be used.

(Iii) Preferably, the molecular weight regulators are mercaptans, for example n-octylmercaptane (NOM: n-octylmercaptane), n-dodecylmercaptane (DDM: n-dodecylmercaptane), and t-dodecylmercaptan (TDDM: t-dodecyl mercaptane) can be used by selecting one or more kinds.

The polymerization temperature is very important for adjusting the gel content and swelling degree of the rubber latex, and the selection of the polymerization initiator should also be considered. In order to obtain an acrylonitrile-butadiene-styrene resin having excellent low temperature impact resistance, an average particle diameter of suitable rubber latex is preferably 2600 mm to 5000 mm and a standard deviation of particle size is 25%. In addition, the total gel content is suitably 60 to 95% and the swelling index is about 18 to 40. In this case, when the average particle diameter of the rubbery polymer is 2600 mm 3 or less, the low temperature impact resistance is lowered, and when the average particle diameter is 5000 mm 3 or more, the stability of the polymer decreases when applied to the acrylonitrile-butadiene-styrene resin, thereby producing a large amount of coagulum.

The present invention will be described in more detail with reference to the following examples and comparative examples. However, an Example is for illustrating this invention and is not limited only to these.

EXAMPLE

Example 1

In a nitrogen-substituted polymerization reactor (autoclave) 75 parts by weight of ion-exchanged water, 100 parts by weight of 1,3-butadiene as monomer, 2.0 parts by weight of potassium rosin salt as emulsifier, 0.4 parts by weight of potassium oleate salt, potassium carbonate as electrolyte K ₂ CO ₃ ) 2.0 parts by weight, 0.3 parts by weight of tertiary dodecyl mercaptan (TDDM) as a molecular weight regulator, 0.2 parts by weight of potassium persulfate as a polymerization initiator were reacted at a reaction temperature of 70 ℃ for 10 hours. When the polymerization conversion rate of the reactants is 50%, 0.3 parts by weight of AQUARON HS-10, which is a reaction emulsifier, is added in a batch, and the temperature is increased to 75 ° C. for 20 hours. This terminated tlu rubber latex.

Example 2

75 parts by weight of ion-exchanged water in a nitrogen-substituted polymerization reactor, 100 parts by weight of 1,3-butadiene as monomer, 2.0 parts by weight of potassium rosin salt as emulsifier, 0.4 parts by weight of potassium oleate salt, AQUARON HS-10 0.1 as reactive emulsifier Parts by weight, 2.0 parts by weight of potassium carbonate as electrolyte, 0.3 parts by weight of tertiary dodecylmercaptan as molecular weight regulator, 0.2 parts by weight of potassium persulfate as polymerization initiator and reacted for 10 hours at a reaction temperature of 70 ° C, resulting in 90% polymerization conversion. When the polymerization inhibitor was added to terminate the reaction to give a rubber latex.

Example 3

75 parts by weight of ion-exchanged water in a nitrogen-substituted polymerization reactor, 100 parts by weight of 1,3-butadiene as monomer, 2.0 parts by weight of potassium rosin salt as emulsifier, 0.4 parts by weight of potassium oleate salt, 2.0 parts by weight of potassium carbonate as electrolyte, molecular weight 0.3 parts by weight of tertiary dodecyl mercaptan as a regulator and 0.2 parts by weight of potassium persulfate as a polymerization initiator were collectively administered and reacted at a reaction temperature of 70 ° C. for 10 hours. When the polymerization conversion rate of the reactants is 50%, 0.1 parts by weight of tertiary dodecylmercaptan, 0.4 parts by weight of potassium rosinate, and 3 parts by weight of AQUARON HS-10 which is a reaction emulsifier are continuously administered, and the temperature is raised to 75 ° C. for 20 hours. After the polymerization conversion was 90%, the polymerization inhibitor was added and the reaction was terminated to obtain a rubber latex.

Example 4

75 parts by weight of ion-exchanged water in a nitrogen-substituted polymerization reactor, 80 parts by weight of 1,3-butadiene as monomer, 2.0 parts by weight of potassium rosin acid salt as emulsifier, 0.4 parts by weight of potassium oleate salt, 2.0 parts by weight of potassium carbonate as electrolyte, molecular weight 0.3 parts by weight of tertiary dodecyl mercaptan as a regulator and 0.2 parts by weight of potassium persulfate as a polymerization initiator were collectively administered and reacted at a reaction temperature of 70 ° C. for 10 hours. When the polymerization conversion rate of the reactant is 50%, 20 parts by weight of 1,3-butadiene, 0.4 parts by weight of potassium rosin acid, 0.2 parts by weight of AQUARON HS-10 which is a reaction emulsifier are added, and the temperature is raised to 75 ° C. for 20 hours. When the polymerization conversion rate was 90%, a polymerization inhibitor was added and the reaction was terminated to obtain a rubber latex.

Comparative Example 1

75 parts by weight of ion-exchanged water in a nitrogen-substituted polymerization reactor, 100 parts by weight of 1,3-butadiene as monomer, 2.0 parts by weight of potassium rosin salt as emulsifier, 0.4 parts by weight of potassium oleate salt, 2.0 parts by weight of potassium carbonate as electrolyte, molecular weight 0.3 parts by weight of tertiary dodecyl mercaptan as a control agent and 0.2 parts by weight of potassium persulfate as a polymerization initiator were reacted at a reaction temperature of 70 ° C. for 10 hours, and when the polymerization conversion rate reached 90%, a polymerization inhibitor was added to terminate the reaction. To give a rubber latex.

Comparative Example 2

75 parts by weight of ion-exchanged water in a nitrogen-substituted polymerization reactor, 80 parts by weight of 1,3-butadiene as monomer, 2.0 parts by weight of potassium rosin acid salt as emulsifier, 0.4 parts by weight of potassium oleate salt, 2.0 parts by weight of potassium carbonate as electrolyte, molecular weight 0.3 parts by weight of tertiary dodecyl mercaptan as a regulator and 0.2 parts by weight of potassium persulfate as a polymerization initiator were collectively administered and reacted at a reaction temperature of 70 ° C. for 10 hours. When the polymerization conversion rate of the reactants is 50%, 20 parts by weight of 1,3-butadiene and 0.4 parts by weight of potassium rosinate are added and the temperature is increased to 75 ° C. for 20 hours, and the polymerization inhibitor is 90%. Charged and the reaction was terminated to give a rubber latex.

The gel content and swelling index, particle size and particle size distribution, and the resulting coagulum of the rubber latex obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were prepared by the following methods a), b), and c). Measured.

A) gel content and swelling index

The rubbery polymer latex was coagulated with dilute acid or metal salt, washed and dried in a vacuum oven at 60 ° C. for 24 hours. After the rubber mass obtained by the above process was finely chopped, 1 g of rubber fragments were put in 100 g of toluene and stored in a dark room at room temperature for 48 hours. This was separated into a sol and a gel and the gel content and swelling index were measured according to the following Equations 1 and 2, and the results are shown in Table 1.

[Equation 1]

[Equation 2]

B) particle size and particle size distribution

It was measured using the Nicomp 370HPL by the dynamic laser light scattering method.

C) produced coagulum;

It measured by the following formula (3).

TABLE 1

division Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Dosing method Batch administration Ion exchange water 75 75 75 75 75 75 1,3-butadiene 100 100 100 80 100 80 Rosin acid potassium salt 2.0 2.0 2.0 2.0 2.0 2.0 Potassium oleate 0.4 0.4 0.4 0.4 0.4 0.4 HS-10 - 0.1 - - - - Potassium carbonate 2.0 2.0 2.0 2.0 2.0 2.0 Class 3 dodecyl mercaptan 0.3 0.3 0.3 0.3 0.3 0.3 Potassium persulfate 0.2 0.2 0.2 0.2 0.2 0.2 Dosing time 10 hours - 10 hours 10 hours - 10 hours Dosing method Batch administration - Continuous administration Continuous administration - Continuous administration 1,3-butadiene - - - 20 - 20 Class 3 dodecyl mercaptan - - 0.1 - - - Potassium Rosinate - - 0.4 0.4 - 0.4 HS-10 0.3 - 3 0.2 - - Polymerization Conversion Rate (%) 91 90 92 91 91 90 Gel content (%) 66 75 63 68 69 75 Swelling index 27 24 26 23 24 23 Particle diameter 3000 2500 2800 2900 3000 2900 Product coagulant (%) 0.002 0.002 0.003 0.002 0.023 0.012

As shown in Table 1, in Examples 1, 2, 3, and 4 to which the reactive emulsifier was added, it was confirmed that the swelling index was larger than that of Comparative Examples 1 and 2, and the coagulation product was less produced. In addition, when the monomer was added and the polymerization conversion was 30 to 70% of the total compound, it was found that when the reactive emulsifier was added, coagulation was less produced than when the monomer and the reactive emulsifier were added simultaneously.

[Example]

Example 1

18 parts by weight of the rubber latex obtained in Example 1 was added to a nitrogen-substituted polymerization reactor, 80 parts by weight of ion-exchanged water, 0.2 parts by weight of sodium oleate emulsifier, 14.38 parts by weight of methyl methacrylate, 5.62 parts by weight of styrene, and acrylonitrile. 2.5 parts by weight, tertiary dodecyl mercaptan 0.2 part by weight, sodium pyrophosphate 0.048 part by weight, dextrose 0.012 part by weight, ferrous sulfide 0.001 part by weight, cumene hydroperoxide 0.04 part by weight at 50 ℃ and the reaction temperature Reacted while raising to 73 degreeC over 2 hours. Here, 70 parts by weight of ion-exchanged water, 0.4 parts by weight of sodium oleate, 43.12 parts by weight of methyl methacrylate, 16.88 parts by weight of styrene, 7.5 parts by weight of acrylonitrile, 0.25 parts by weight of tertiary dodecyl mercaptan, and 0.048 parts by weight of sodium phosphate , 0.012 parts by weight of dextrose, 0.001 parts by weight of ferrous sulfide, and 0.10 parts by weight of cumene hydroperoxide were continuously administered for 4 hours, and then heated to 76 ° C. and aged for 1 hour to complete the reaction. . At this time, the polymerization conversion was 99.5% and the solid coagulum was 0.05%.

Example 2

Was prepared in the same manner as in Example 1, using the rubber latex obtained in Example 2.

Example 3

Was prepared in the same manner as in Example 1, using the rubber latex obtained in Example 3.

Example 4

Was prepared in the same manner as in Example 1, using the rubber latex obtained in Example 4.

Example 5

In the same manner as in Use Example 1, was prepared using the rubber latex obtained in Comparative Example 1.

Use Example 6

Was prepared in the same manner as in Example 1, using the rubber latex obtained in Comparative Example 2.

The graft copolymers prepared in Examples 1 to 6 were coagulated with 5.0 parts by weight of an aqueous calcium chloride solution, and the powders obtained by washing were shown in Table 2 below.

TABLE 2

division Example 1 Example 2 Example 3 Example 4 Example 5 Use Example 6 Notch Izod Impact Strength ASTM, D-256 18 14 16 17 18 17 Flow Index ASTM, D-1238 20 16 19 19 20 18 Haze value ASTM, D-1003 2.5 1.5 2.3 2.4 4.0 3.8 Product coagulation after polymerization 0.023 0.036 0.013 0.022 0.053 0.048 Latex Cohesion in Calcium Chloride good good Bad good good good

As shown in Table 2, in Examples 1, 2, 3, and 4, which are graft copolymers prepared using a rubber latex prepared by adding a reactive emulsifier, use example 5 without a reactive emulsifier was added. It was confirmed that the haze value was superior to, and 6, and the formation of coagulum after polymerization was less.

The production method of the present invention can increase the stability to reduce the formation of coagulum and to produce a rubber latex having a narrow rubber particle size distribution, as well as to prepare a transparent acrylonitrile-butadiene-styrene resin excellent in high impact and high transparency. It is possible to provide a rubber latex with excellent stability.

Claims (13)

In the method for producing a rubber latex having excellent stability, Iii) conjugated diene compound monomer Ii) emulsion polymerization by adding a reactive emulsifier Method for producing a stable rubber latex comprising a. The method of claim 1, Iii) 100 parts by weight of the conjugated diene compound monomer; Ii) adding 0.01 to 3.0 parts by weight of a reactive emulsifier to polymerize by emulsion polymerization. Steps Method for producing a stable rubber latex comprising a. The method of claim 1, a) in the reactor Iii) 50 to 100 parts by weight of the conjugated diene compound monomer; Ii) 0.5 parts by weight or less of a reactive emulsifier; V) 1 to 4 parts by weight of a non-reactive emulsifier; Iii) 0.2 to 1.5 parts by weight of a polymerization initiator; V) 0.5 to 2 parts by weight of electrolyte; Iii) 0.1 to 0.5 parts by weight of a molecular weight modifier; And Viii) 75 to 100 parts by weight of ion-exchanged water Dosing in a batch to react at 65 to 75 ° C. for 4 to 15 hours; b) reactants of step a) V) 50 parts by weight or less of the remaining conjugated diene compound monomers; And Iii) 0.1 to 0.5 parts by weight of molecular weight regulator To batch or continuous dosing and reacted at 70 to 85 ° C. for 10 to 20 hours. step; And c) the polymerization conversion rate of the reactant of step b) is 30-70% of the total compound Ii) 0.01 to 3.0 parts by weight of a reactive emulsifier Steps to apply Excellent rubber latex manufacturing method comprising a. The method according to any one of claims 1 to 3, Ii) an anionic emulsifier in which the reactive emulsifier has an allyl group of the sulfate salt of polyoxyethylene allyl glycidic nonylphenyl ether; Neutral emulsifiers having an allyl group of the polyoxyethylene allylglycidyl nonylphenyl ether series; Anionic emulsifier which has a (meth) acryloyl group; Neutral emulsifiers having a (meth) acryloyl group; Anionic emulsifiers having a propene group of an aluminum sulfate salt of polyoxyethylene allylglycidyl nonyl propenyl phenyl ether; A method for producing acrylonitrile-butadiene-styrene latex selected from the group consisting of neutral emulsifiers. The method of claim 3, wherein Iii) Preparation of rubber latex having excellent stability, wherein the unreacted emulsifier is selected from the group consisting of alkyl aryl sulfonates, alkali methyl alkyl sulfates, sulfonated alkyl esters, fatty acid soaps, and alkali salts of rosin acid. Way. The method according to any one of claims 1 to 3, (Iii) Stability of conjugated diene compound monomers used alone or in combination with aromatic vinyl compounds such as styrene and α-methylstyrene, and vinyl cyan compounds such as acrylonitrile and used within 15 parts by weight of the total monomer mixture. This excellent rubber latex manufacturing method. The method according to any one of claims 1 to 3, Iii) a method for producing a rubber latex having excellent stability wherein the conjugated diene compound is selected from the group consisting of 1,3-butadiene, isoprene, chloroprene and pyreriden. The method of claim 3, wherein Iii) Preparation of rubber latex having excellent stability, wherein the unreacted emulsifier is selected from the group consisting of alkyl aryl sulfonates, alkali methyl alkyl sulfates, sulfonated alkyl esters, fatty acid soaps, and alkali salts of rosin acid. Way. The method of claim 3, wherein Iii) the polymerization initiator is sodium persulfate or water-soluble persulfate of potassium persulfate; Fat-soluble polymerization initiators of cumenehydro peroxide, diisopropyl benzene hydroperoxide, azobis isobutylonitrile, tertiary butyl hydroperoxide, paramethane hydroperoxide, or benzoyl peroxide; And an oxidation-reduction type polymerization initiator, and at least one selected from the group consisting of rubber latex having excellent stability. The method of claim 3, wherein I) KCl, NaCl, KHCO ₃ , NaHCO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , KHSO ₃ , NaHSO ₃ , K ₄ P ₂ O ₇ , Na ₄ P ₂ O ₇ , K ₃ PO ₄ , A method for producing a rubber latex having excellent stability selected from the group consisting of Na ₃ PO ₄ , Na ₂ HPO ₄ , and Na ₂ HPO ₄ . The method of claim 3, wherein (Iii) A method for producing a rubber latex having excellent stability, wherein the molecular weight modifier is at least one selected from the group consisting of n-octyl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan. A rubber latex having an average particle diameter of 2600 to 5000 mm 3, a particle size standard deviation of 25%, a total gel content of 60 to 95% by weight, and an swelling index of 18 to 40, produced by the method according to any one of claims 1 to 3. The acrylonitrile-butadiene-styrene resin excellent in the stability manufactured using the rubber latex of Claim 12.