JP7031383B2 - How to make synthetic rubber latex - Google Patents

Description

The present invention relates to a method for producing a latex of synthetic rubber, and more particularly to a method for producing a latex of synthetic rubber, which enables production in a short time while achieving a high yield.

Conventionally, it is known that a latex composition containing a latex of natural rubber is dip-molded to obtain a dip-molded body to be used in contact with a human body such as a nipple, a balloon, a glove, a balloon, or a sack. However, since the latex of natural rubber contains a protein that causes allergic symptoms in the human body, there may be a problem as a dip molded product that comes into direct contact with a biological mucous membrane or an organ. Therefore, studies have been made on using synthetic rubber latex instead of natural rubber latex.

For example, in Patent Document 1, as a method for producing such a latex of synthetic rubber, an emulsion is obtained by mixing a solution of synthetic rubber in which synthetic rubber is dissolved in an organic solvent and an aqueous solution of an emulsifier. Disclosed is a method for removing an organic solvent by heating the obtained emulsion under reduced pressure conditions at a temperature higher than the boiling point of the organic solvent. However, the technique of Patent Document 1 has a problem that it takes time to remove the organic solvent, and therefore the productivity is inferior.

Japanese Patent No. 5260738

An object of the present invention is to provide a method for producing a latex of synthetic rubber, which can be produced in a short time while achieving a high yield.

As a result of diligent research to solve the above problems, the present inventors continuously put a synthetic rubber solution or dispersion in which synthetic rubber is dissolved or dispersed in an organic solvent and an aqueous solution of an emulsifier into a mixing device. Removal of organic solvent in the container while continuously transferring the emulsion obtained continuously by supplying and mixing into a container adjusted to a pressure condition of -0.005 to 0 MPa at a gauge pressure. At this time, it was found that the above object can be achieved by removing the organic solvent while spraying the defoaming agent aqueous solution on the emulsion transferred into the container. It came to be completed.

That is, according to the present invention, a solution or dispersion of synthetic rubber in which synthetic rubber is dissolved or dispersed in an organic solvent and an aqueous solution of an emulsifier are continuously supplied to a mixing device and mixed to emulsify. The emulsification process to continuously obtain the liquid and
The organic solvent is usually removed in the container while continuously transferring the emulsified liquid continuously obtained in the emulsification step into a container adjusted to a pressure condition of −0.005 to 0 MPa with a gauge pressure. Equipped with a pressure relief process,
Provided is a method for producing a synthetic rubber latex, which removes an organic solvent while spraying an aqueous solution of an antifoaming agent on the liquid surface of the emulsion transferred into the container in the normal pressure removing step.

In the method for producing a latex of synthetic rubber of the present invention, an aqueous solution of an antifoaming agent is sprayed onto the surface of an emulsion that has undergone the normal pressure removal step under a reduced pressure condition of −0.01 MPa or less at a gauge pressure. It is preferable to further include a vacuum removing step of removing the organic solvent.
In the method for producing a latex of synthetic rubber of the present invention, it is preferable to use an aqueous solution of the defoaming agent having a concentration of the defoaming agent of 0.005 to 0.1% by weight.
In the method for producing a latex of synthetic rubber of the present invention, it is preferable to use an aqueous solution of the defoaming agent containing a silicon-based defoaming agent.
In the method for producing a latex of synthetic rubber of the present invention, in the normal pressure removing step, the temperature of the emulsion is set to a temperature range of Tb-10 to Tb + 5 ° C. with respect to the boiling point Tb of the organic solvent under atmospheric pressure. It is preferable to remove the organic solvent while controlling the temperature.
In the method for producing a latex of synthetic rubber of the present invention, it is preferable to use an aqueous solution of the emulsifier containing a fatty acid salt and / or an alkylbenzene sulfonate.

According to the method for producing a latex of synthetic rubber of the present invention, it is possible to produce a latex in a short time while achieving a high yield, which makes it possible to improve productivity.

FIG. 1 is a diagram showing an example of an emulsifying device used in the method for producing a latex of synthetic rubber of the present invention.

The method for producing a latex of synthetic rubber of the synthetic rubber of the present invention is
An emulsification step in which an emulsified solution is continuously obtained by continuously supplying and mixing a solution or dispersion of synthetic rubber in which synthetic rubber is dissolved or dispersed in an organic solvent and an aqueous solution of an emulsifier to a mixing device. When,
The organic solvent is usually removed in the container while continuously transferring the emulsified liquid continuously obtained in the emulsification step into a container adjusted to a pressure condition of −0.005 to 0 MPa with a gauge pressure. Equipped with a pressure relief process,
In the normal pressure removing step, the organic solvent is removed while spraying an aqueous solution of an antifoaming agent on the liquid surface of the emulsion transferred into the container.

<Emulsification process>
In the emulsification step of the production method of the present invention, a synthetic rubber solution or dispersion in which synthetic rubber is dissolved or dispersed in an organic solvent and an aqueous solution of an emulsifier are continuously supplied to a mixing device and mixed. , Is a step of continuously obtaining an emulsion.

The synthetic rubber solution or dispersion used in the production method of the present invention is not particularly limited as long as it is a solution or dispersion in which synthetic rubber is dissolved or dispersed in an organic solvent.

The synthetic rubber is not particularly limited, but is a homopolymer or copolymer of a conjugated diene monomer such as synthetic polybutadiene, synthetic polyisoprene, and synthetic polychloroprene; a styrene-butadiene copolymer, a styrene-isoprene copolymer, and the like. Conjugate diene monomers such as styrene-isoprene-styrene block copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, acrylonitrile-butadiene-isoprene copolymer, butyl acrylate-butadiene copolymer and this Copolymers with other copolymerizable monomers; acrylate-based (co) polymers and the like can be mentioned. Among these, synthetic polyisoprene and / or styrene-isoprene-styrene block copolymer is preferable because it is excellent in tensile strength and elongation in the case of a film molded body such as a dip molded body.

Hereinafter, the case where the synthetic rubber constituting the solution or dispersion of the synthetic rubber used in the production method of the present invention is a synthetic polyisoprene and / or a styrene-isoprene-styrene block copolymer is illustrated, but the production of the present invention is exemplified. The synthetic rubber solution or dispersion used in the method is not limited to the synthetic polyisoprene and / or the styrene-isoprene-styrene block copolymer solution or dispersion.

The synthetic polyisoprene may be a homopolymer of isoprene, or may be a copolymer of isoprene and another ethylenically unsaturated monomer copolymerizable. The content of the isoprene unit in the synthetic polyisoprene is preferably 70% by weight or more with respect to all the monomer units because it is easy to obtain a film molded product such as a dip molded product which is flexible and has excellent tensile strength. It is more preferably 90% by weight or more, further preferably 95% by weight or more, and particularly preferably 100% by weight (a homopolymer of isoprene).

Other ethylenically unsaturated monomers copolymerizable with isoprene include conjugated diene monomers other than isoprene such as butadiene, chloroprene, 1,3-pentadiene; acrylonitrile, methacrylonitrile, fumaronitrile, α-. Ethylene unsaturated nitrile monomers such as chloroacrylonitrile; vinyl aromatic monomers such as styrene and alkylstyrene; methyl (meth) acrylate (meaning "methyl acrylate and / or methyl methacrylate" and below. , (Meta) ethyl acrylate, etc.), Ethyl unsaturated carboxylic acid ester monomer such as (meth) ethyl acrylate, (meth) butyl acrylate, (meth) -2-ethylhexyl acrylate; etc. Can be mentioned. The other ethylenically unsaturated monomers copolymerizable with these isoprenes may be used alone or in combination of two or more.

Synthetic polyisoprene is prepared in an organic solvent using a conventionally known method, for example, a Cheegler-based polymerization catalyst composed of trialkylaluminum-titanium tetrachloride or an alkyllithium polymerization catalyst such as n-butyllithium or sec-butyllithium. And other copolymerizable ethylenically unsaturated monomers used as needed can be polymerized to obtain a solution of synthetic polyisoprene in which synthetic polyisoprene is dissolved in an organic solvent. .. The synthetic polyisoprene solution obtained by solution polymerization may be used as it is in the emulsification step, but the solid synthetic polyisoprene is taken out from the solution obtained by solution polymerization and then dissolved in an organic solvent. , May be used.

Examples of the organic solvent used for polymerization include aromatic hydrocarbon solvents such as benzene, toluene and xylene; alicyclic hydrocarbon solvents such as cyclopentane, cyclopentene, cyclohexane and cyclohexene; butane, pentane, hexane and heptane and the like. Hydrocarbon solvents of the above; halogenated hydrocarbon solvents such as methylene chloride, chloroform, ethylene dichloride; and the like can be mentioned. Of these, an aliphatic hydrocarbon solvent is preferable, and butane is particularly preferable.

As the isoprene unit in the synthetic polyisoprene, there are four types, a cis bond unit, a trans bond unit, a 1,2-vinyl bond unit, and a 3,4-vinyl bond unit, depending on the isoprene binding state. From the viewpoint of improving the tensile strength of the obtained film-molded article such as a dip-molded article, the content ratio of the cis-bonding unit in the isoprene unit contained in the synthetic polyisoprene is preferably 70% by weight or more with respect to the total isoprene unit. It is more preferably 90% by weight or more, still more preferably 95% by weight or more.

The weight average molecular weight of the synthetic polyisoprene is preferably 10,000 to 5,000,000, more preferably 500,000 to 5,000,000, still more preferably, in terms of standard polystyrene by gel permeation chromatography analysis. Is between 800,000 and 3,000,000. By setting the weight average molecular weight of the synthetic polyisoprene in the above range, the tensile strength of the obtained film molded product in the case of a film molded product such as a dip molded product is improved, and the synthetic polyisoprene latex can be easily produced. Tend.

The polymer Mooney viscosity (ML1 + 4, 100 ° C.) of the synthetic polyisoprene is preferably 50 to 80, more preferably 60 to 80, still more preferably 70 to 80.

The styrene-isoprene-styrene block copolymer is a block copolymer of styrene and isoprene. The content ratio of the styrene unit and the isoprene unit in the styrene-isoprene-styrene block copolymer is not particularly limited, but is usually 1:99 to 90:10, preferably 3 in terms of the weight ratio of "styrene unit: isoprene unit". : 97 to 70:30, more preferably 5:95 to 50:50, still more preferably 10:90 to 30:70.

The styrene-isoprene-styrene block copolymer can be prepared by using a conventionally known method, for example, a Cheegler-based polymerization catalyst composed of trialkylaluminum-titanium tetrachloride or an alkyllithium polymerization catalyst such as n-butyllithium or sec-butyllithium. By block copolymerizing isoprene and styrene in an organic solvent, a styrene-isoprene-styrene block copolymer can be obtained as a solution of a styrene-isoprene-styrene block copolymer in which the styrene-isoprene-styrene block copolymer is dissolved in the organic solvent. can. The solution of the styrene-isoprene-styrene block copolymer obtained by the block copolymer may be used as it is in the emulsification step, but the solid styrene-isoprene-styrene block from the solution obtained by the block copolymer may be used as it is. After taking out the copolymer, it may be dissolved in an organic solvent and used. Moreover, as the organic solvent used for polymerization, the same thing as the above-mentioned synthetic isoprene can be mentioned.

The content ratio of the cis bond unit in the isoprene unit contained in the styrene-isoprene-styrene block copolymer is based on the total isoprene unit from the viewpoint of improving the tensile strength of the film-molded article such as the obtained dip-molded article. It is preferably 90% by weight or more, more preferably 95% by weight or more, and further preferably 98% by weight or more.

The weight average molecular weight of the styrene-isoprene-styrene block copolymer is preferably 10,000 to 1,000,000, more preferably 50,000 to 500, in terms of standard polystyrene by gel permeation chromatography analysis. 000, more preferably 100,000 to 300,000. By setting the weight average molecular weight of the styrene-isoprene-styrene block copolymer in the above range, the tensile strength of the obtained film molded body in the case of a film molded body such as a dip molded body is improved, and styrene-isoprene is used. -Styrene block copolymer latex tends to be easier to produce.

The polymer Mooney viscosity (ML1 + 4, 100 ° C.) of the styrene-isoprene-styrene block copolymer is preferably 50 to 80, more preferably 60 to 80, and even more preferably 70 to 80.

The content ratio of the synthetic rubber in the solution or dispersion of the synthetic rubber used in the emulsification step of the production method of the present invention is not particularly limited, but is preferably 3 to 30% by weight, more preferably 5 to 20% by weight. More preferably, it is 7 to 15% by weight.

The emulsifier constituting the aqueous solution of the emulsifier used in the emulsification step of the production method of the present invention is not particularly limited, but an anionic emulsifier can be preferably used. Examples of the anionic emulsifier include fatty acid salts such as sodium laurate, potassium myristate, sodium palmitate, potassium oleate, sodium linolenate, sodium rosinate, and potassium rosinate; sodium dodecylbenzenesulfonate, dodecylbenzenesulfonic acid. Alkylbenzene sulfonates such as potassium, sodium decylbenzenesulfonate, potassium decylbenzenesulfonate, sodium cetylbenzenesulfonate, potassium cetylbenzenesulfonate; sodium di (2-ethylhexyl) sulfosuccinate, di (2-ethylhexyl) sulfosuccinic acid Alkyl sulfosuccinates such as potassium and sodium dioctyl sulfosuccinate; alkyl sulfates such as sodium lauryl sulfate and potassium lauryl sulfate; polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene lauryl ether sulfate and potassium polyoxyethylene lauryl ether sulfate. Esther salts; monoalkyl phosphates such as sodium lauryl phosphate and potassium lauryl phosphate; and the like.

Among these anionic emulsifiers, fatty acid salts, alkylbenzene sulfonates, alkylsulfosuccinates, alkylsulfate esters and polyoxyethylene alkylether sulfates are preferred, and the formation of aggregates in the resulting synthetic rubber latex is more favorable. Fatty acid salts and alkylbenzene sulfonates are more preferred, fatty acid salts are even more preferred, sodium rosinate, rosinate, from the perspective of being able to adequately prevent and further enhance the stability of the resulting synthetic rubber latex. Potassium is particularly preferred. It is also preferable to use a fatty acid salt in combination with an alkylbenzene sulfonate.

The content ratio of the emulsifier in the aqueous solution of the emulsifier used in the emulsification step of the production method of the present invention is not particularly limited, but is preferably 0.1 to 5% by weight, more preferably 0.3 to 3% by weight, and further. It is preferably 0.5 to 2% by weight.

Then, in the emulsification step of the production method of the present invention, a solution or dispersion of synthetic rubber in which such synthetic rubber is dissolved or dispersed in an organic solvent and an aqueous solution of an emulsifier are continuously supplied to a mixing device. And by mixing, an emulsion is continuously obtained.

Here, FIG. 1 is a diagram showing an example of an emulsifying device used in the method for producing a latex of synthetic rubber of the present invention. As shown in FIG. 1, the emulsification device shown in FIG. 1 includes a polymer tank 10, an emulsifier tank 20, a mixing device 30, a storage tank 40, a valve 50, and a concentrator 60. ..

Hereinafter, the emulsification step of the production method of the present invention will be described with reference to FIG. 1, but the present invention is not particularly limited to the embodiment using the emulsification apparatus shown in FIG.

That is, to explain with reference to FIG. 1, in the emulsification step of the production method of the present invention, a solution or dispersion of synthetic rubber is continuously applied from the polymer tank 10 and an aqueous solution of the emulsifier is continuously applied from the emulsifier tank 20. In the mixing device 30, the solution or dispersion of the synthetic rubber and the aqueous solution of the emulsifier are continuously mixed to obtain an emulsion continuously. Then, in the production method of the present invention, the obtained emulsion is continuously supplied to the storage tank 40.

In the emulsification step of the production method of the present invention, when the solution of the synthetic rubber or the dispersion liquid and the aqueous solution of the emulsifier are continuously sent to the mixing device 30, the supply ratio thereof is not particularly limited, but the emulsification of the synthetic rubber is performed. From the viewpoint of being able to proceed more appropriately, the volume ratio of "synthetic rubber solution or dispersion: emulsion of emulsifier" is preferably 1: 2 to 1: 0.3, more preferably 1: 1.5. It is ~ 1: 0.5, more preferably 1: 1 ~ 1: 0.7.

The method for continuously sending the synthetic rubber solution or dispersion and the emulsifier aqueous solution from the polymer tank 10 and the emulsifier tank 20 to the mixing device 30 is not particularly limited, but the synthetic rubber solution or dispersion and the synthetic rubber solution and the dispersion are not particularly limited. The aqueous solution of the emulsifier may be sent directly to the mixing device 30 by a pump, or the premixing device may be provided with a premixing device such as a line mixer on the upstream side of the mixing device 30. The premixed state may be sent to the mixing device 30 in the premixed state.

The mixing device 30 may be any device capable of continuously mixing, and is not particularly limited. For example, the product name "TK Pipeline Homo Mixer" (manufactured by Tokushu Kagaku Kogyo Co., Ltd.) and the product name "colloid" are used. Mill "(manufactured by Shinko Pantech), product name" Slasher "(manufactured by Nippon Coke Industries), product name" Trigonal Wet Miller "(manufactured by Mitsui Miike Kakoki), product name" Cavitron "(Eurotech) , Product name "Milder" (manufactured by Pacific Kiko Co., Ltd.), product name "Fine Flow Mill" (manufactured by Pacific Kiko Co., Ltd.), etc. can be used. The conditions for the mixing operation by the mixing device 30 are not particularly limited, and the processing temperature, processing time, and the like may be appropriately selected so as to obtain a desired dispersion state.

In the emulsification step of the production method of the present invention, the synthetic rubber solution or dispersion and the emulsifier when the synthetic rubber solution or dispersion and the emulsifier aqueous solution are continuously sent to the mixing device 30 for mixing. The temperature of the aqueous solution of the above is not particularly limited, but is preferably 20 to 100 ° C., more preferably 40 to 90 ° C., and even more preferably 60 to 80 ° C. from the viewpoint that emulsification can be performed satisfactorily. The temperature at which these are mixed is the temperature at which the synthetic rubber solution or dispersion is stored in the polymer tank 10 and the emulsifier aqueous solution is used as the emulsifier tank so that the mixing temperature becomes a desired temperature. The temperature at the time of storage in 20 may be controlled by adjusting each. For example, when a solution or dispersion of synthetic rubber at 60 ° C. and an aqueous solution of an emulsifier at 60 ° C. are mixed in the mixing device 30, when the solution or dispersion of synthetic rubber is stored in the polymer tank 10. 60 ° C., and the temperature at which the aqueous solution of the emulsifier is stored in the emulsifier tank 20 may be 60 ° C.

<Normal pressure removal process>
In the normal pressure removing step of the production method of the present invention, the emulsion continuously obtained in the above-mentioned emulsification step is continuously transferred into a container adjusted to a pressure condition of −0.005 to 0 MPa with a gauge pressure. However, it is a step of removing the organic solvent contained in the emulsion (that is, the organic solvent derived from the synthetic rubber solution or the dispersion liquid) in the container. Further, in the normal pressure removing step of the production method of the present invention, when the organic solvent contained in the emulsion is removed in the container, the defoaming agent is applied to the liquid surface of the emulsion transferred into the container. The organic solvent is removed while spraying the aqueous solution. The removal of the organic solvent from the emulsion in the normal pressure removing step of the production method of the present invention is carried out while continuously transferring the emulsion continuously obtained in the above-mentioned emulsification step into the container. Therefore, it is usually performed almost at the same time as the above-mentioned emulsification step.
In the following, a specific embodiment of the normal pressure removing step of the production method of the present invention will be described with reference to FIG. 1, but the present invention is particularly limited to the embodiment using the emulsifying apparatus shown in FIG. It's not a thing.

That is, to explain a specific embodiment of the normal pressure removing step of the manufacturing method of the present invention with reference to FIG. 1, in the normal pressure removing step, the emulsified liquid continuously sent from the mixing device 30 is stored. By controlling the pressure in the storage tank 40 to a pressure of −0.005 to 0 MPa with a gauge pressure while continuously receiving the emulsion in the tank 40, the organic solvent contained in the received emulsion is removed at normal pressure. Here, in the normal pressure removing step of the manufacturing method of the present invention, the valve 50 is opened in order to remove the organic solvent under normal pressure, whereby the inside of the storage tank 40 becomes an open system. Therefore, the organic solvent removed from the emulsion under normal pressure can be recovered by the concentrator 60 through the pipe on the valve 50 side. Alternatively, in the normal pressure removing step of the manufacturing method of the present invention, the pressure in the storage tank 40 is increased by the pressure reducing pump in a state where the pressure reducing pump is connected to the downstream side of the concentrator 60 and the valve 50 is “open”. In such a state that the gauge pressure is maintained at −0.005 to 0 MPa, and in such a state, the organic solvent removed under normal pressure from the emulsion is similarly recovered by the concentrator 60. May be good.

The pressure in the normal pressure removing step is −0.005 to 0 MPa (gauge pressure), preferably −0.002 to 0 MPa (gauge pressure), and atmospheric pressure (0 MPa (0 MPa) because it is easy to control. Gauge pressure)) is particularly preferable.

Further, in the normal pressure removing step of the manufacturing method of the present invention, the normal pressure removing of the organic solvent is performed while spraying an aqueous solution of a defoaming agent on the liquid surface of the emulsion transferred into the storage tank 40. As a result, when the emulsified liquid is supplied into the storage tank 40, the emulsified liquid foams, so that a part of the emulsified liquid enters the concentrator 60 from the storage tank 40, and the yield is lowered. It is possible to improve the removal efficiency of the organic solvent while effectively preventing the problem of the organic solvent. As a result, the organic solvent contained in the emulsion can be removed in a short time while achieving a high yield. In particular, in the normal pressure removing step of the production method of the present invention, since the aqueous solution of the defoaming agent is added by spraying on the liquid surface of the emulsion, the defoaming agent can be used even in a relatively small amount. The effect of the addition of the emulsion can be made sufficient, and the addition of the defoaming agent effectively suppresses the occurrence of problems such as the generation of agglomerates in the latex of the obtained synthetic rubber, while effectively suppressing the occurrence of the emulsion. It is possible to appropriately suppress foaming.

As the defoaming agent contained in the aqueous solution of the defoaming agent, known defoaming agents such as mineral oil-based defoaming agents, silicon-based defoaming agents, and polymer-based defoaming agents can be used. A silicon-based defoaming agent is preferable from the viewpoint that the generation of agglomerates is unlikely to occur. The concentration of the defoaming agent in the aqueous solution of the defoaming agent is preferably 0.005 to 0.1% by weight, more preferably 0.008 to 0.05% by weight, still more preferably 0.01. ~ 0.02% by weight. By setting the concentration of the defoaming agent in the above range, the effect of adding the defoaming agent can be further enhanced while the stability of the obtained synthetic rubber latex is sufficiently stable.

The spraying method for spraying the aqueous solution of the defoaming agent onto the liquid surface of the emulsion is not particularly limited, but a spraying device provided at the upper part of the storage tank 40 (for example, a pipe having a spray nozzle at the end) is used. A method of spraying is preferable by pressurizing with a pressure of preferably 0.05 to 0.2 MPa, more preferably 0.1 to 0.18 MPa. Further, the spraying of the aqueous solution of the defoaming agent is continuously performed from the start of supply of the emulsion to the storage tank 40 from the mixing device 30 to the end of supply from the viewpoint of suppressing the foaming of the emulsion. This is preferable, and the effect of suppressing foaming of the emulsion can be further enhanced. In this case, the spraying of the defoaming agent aqueous solution is substantially continuous, specifically, the storage tank 40 is constantly filled with the mist of the defoaming agent aqueous solution. Such an embodiment may be used, and the aqueous solution of the defoaming agent may be partially sprayed intermittently.

Further, when spraying the aqueous solution of the defoaming agent, the yield is determined from the viewpoint of the effect of suppressing foaming of the emulsion and the synthetic rubber contained in the emulsion adhering to the wall surface of the storage tank 40. From the viewpoint of suppressing the decrease, it is preferable to spray the emulsion on the entire surface of the emulsion. The number of spraying devices provided in the storage tank 40 may be such that the aqueous solution of the defoaming agent can be sprayed on the entire surface of the emulsion, and is not particularly limited, but is usually 1 to 4. It is a degree.

Further, in the normal pressure removing step of the production method of the present invention, the temperature of the emulsion when the organic solvent contained in the emulsion is removed at normal pressure in the storage tank 40 is the temperature of the organic solvent contained in the emulsion. It is preferable to control the boiling point Tb of (that is, an organic solvent derived from a synthetic rubber solution or a dispersion) in the range of Tb-10 to Tb + 5 ° C., and Tb-5 to Tb + 2 ° C. It is more preferable to control the temperature within the range of Tb-1 to Tb + 0.5 ° C., and it is further preferable to control the temperature within the range of Tb-1 to Tb + 0.5 ° C. By removing the organic solvent in the normal pressure removing step at such a temperature, the efficiency of removing the organic solvent can be further improved while appropriately preventing foaming of the emulsion.

Further, in the normal pressure removing step of the manufacturing method of the present invention, the supply speed (m ³ / hr) of the emulsified liquid from the mixing device 30 to the storage tank 40 is divided by the volume (m ³ ) in the storage tank 40. Transfer rate (acceptance rate) (1 / hr) of the emulsion to the storage tank 40, that is, "transfer rate of the emulsion to the storage tank 40 (1 / hr) = from the mixing device 30 to the storage tank 40". The supply rate of the emulsion to the emulsion (m ³ / hr) ÷ the volume in the storage tank 40 (m ³ ) ”is preferably 0.01 to 0.5, more preferably 0.02 to 0.2. More preferably, it is 0.08 to 0.12. In the production method of the present invention, the normal pressure removal of the organic solvent in the normal pressure removal step is performed while spraying the aqueous solution of the defoaming agent on the liquid surface of the emulsion, so that the supply rate of the emulsion is controlled. Even if it is relatively fast, it is possible to suppress a problem that a part of the emulsified liquid enters the concentrator 60 from the storage tank 40, whereby the time required for removing the organic solvent is appropriate. Can be shortened to. As is clear from the above definition, for example, when the transfer rate of the emulsion to the storage tank 40 is 0.1 (1 / hr), the amount of the emulsion transferred to the storage tank 40 and the amount of the emulsion transferred to the storage tank 40. When the volume of the storage tank 40 becomes equal in 10 hours and the transfer speed of the emulsion to the storage tank 40 is 0.2 (1 / hr), the storage tank 40 The speed is such that the amount of the emulsion transferred to and the volume of the storage tank 40 become equal in 5 hours.

The method of transferring the emulsified liquid to the storage tank 40 within the above range is not particularly limited, but for example, a synthetic rubber solution or a dispersion liquid can be obtained from the polymer tank 10 or an emulsifier tank 20. Examples thereof include a method of adjusting the supply rate when the aqueous solution of the emulsifier is continuously sent to the mixing device 30, and a method of adjusting the size of the storage tank 40 to be used.

Further, in the normal pressure removing step of the production method of the present invention, the emulsified liquid continuously sent from the mixing device 30 is continuously received in the storage tank 40, and the emulsified liquid received in the storage tank 40. It is preferable to continue the operation of removing the organic solvent contained therein under normal pressure until the amount of the emulsion supplied to the storage tank 40 becomes 70 to 140% by volume with respect to the volume of the storage tank 40. , It is more preferable to continue until the amount is 80 to 130% by volume, and further preferably to continue until the amount is 90 to 120% by volume. By continuing the above operation until the amount of the emulsified liquid supplied to the storage tank 40 reaches the above-mentioned amount, the emulsified liquid foams, and a part of the emulsified liquid is transferred from the storage tank 40 into the concentrator 60. It is possible to increase the amount of processing in one operation while effectively preventing the problem of entering and reducing the yield, which makes it possible to improve productivity.

In the normal pressure removing step of the production method of the present invention, while continuously receiving the emulsified liquid continuously sent from the mixing device 30 into the storage tank 40, the aqueous solution of the defoaming agent is introduced in the storage tank 40. In order to evaporate the organic solvent contained in the received emulsion while spraying, the amount of the emulsion actually stored in the storage tank 40 after the normal pressure removing step is completed is supplied from the mixing device 30. It is usually less than the amount of emulsion. That is, for example, even when the amount of the emulsion supplied from the mixing device 30 is 90% by volume with respect to the volume of the storage tank 40, the emulsion is continuously supplied from the mixing device 30. Since a part of the organic solvent contained in the emulsion evaporates during the period, the amount of the emulsion actually stored in the storage tank 40 is usually 90% by volume with respect to the volume of the storage tank 40. The amount is less than (for example, about 80% by volume or less). Therefore, even when the amount of the emulsified liquid supplied from the mixing device 30 exceeds 100% by volume (for example, 120% by volume) with respect to the volume of the storage tank 40, it is continuous from the mixing device 30. Since a part of the organic solvent contained in the emulsion is removed under normal pressure while the emulsion is being supplied, the amount of the emulsion actually stored in the storage tank 40 is determined by the storage tank. The amount can be less than 100% by volume with respect to the volume of 40.

In the normal pressure removing step of the manufacturing method of the present invention, the amount of the emulsion supplied to the storage tank 40 may be within the above range, but the inside of the storage tank 40 after the normal pressure removing step is completed. The amount of the emulsion stored in the emulsion (that is, the amount in the storage tank 40 after a part of the organic solvent contained in the emulsion is removed under normal pressure) is preferably 10 with respect to the volume of the storage tank 40. It is ~ 90% by volume, more preferably 20-80% by volume, and most preferably 30-70% by volume. Further, in the normal pressure removing step of the production method of the present invention, 50% by weight or more of the total amount of the organic solvent contained in the emulsion supplied to the storage tank 40 is removed under normal pressure. It is more preferable, and it is more preferable to have an embodiment in which 70% by weight or more is removed under normal pressure, and it is particularly preferable to have an embodiment in which 80% by weight or more is removed under normal pressure. The upper limit is not particularly limited, but is about 98% by weight or less.

<Decompression removal process>
Further, in the production method of the present invention, while spraying an aqueous solution of an antifoaming agent on the liquid surface of the emulsion that has undergone the above-mentioned normal pressure removing step, under a reduced pressure condition of −0.01 MPa or less at a gauge pressure. It is preferable to further include a vacuum removing step of removing the organic solvent contained in the emulsion. In the following, a specific embodiment of the vacuum removal step of the production method of the present invention will be described with reference to FIG. 1, but the present invention is particularly limited to the embodiment using the emulsifying apparatus shown in FIG. is not it.

That is, to explain a specific embodiment of the decompression removal step of the production method of the present invention with reference to FIG. 1, in the decompression removal step, the emulsified liquid that has undergone the above-mentioned normal pressure removal step is stored in the storage tank 40. In this state, the pressure in the storage tank 40 is reduced to −0.01 MPa or less with a gauge pressure to remove the organic solvent contained in the emulsion through the above-mentioned normal pressure removing step under reduced pressure. In the decompression removal step of the manufacturing method of the present invention, for example, the pressure in the storage tank 40 is depressurized by the decompression pump with the decompression pump connected to the downstream side of the concentrator 60 and the valve 50 open. By setting the pressure in the storage tank 40 to less than 700 mmHg, the organic solvent decompressed from the emulsion can be recovered by the concentrator 60 through the pipe on the valve 50 side.

The pressure in the vacuum removing step is −0.01 MPa (gauge pressure) or less, preferably −0.02 MPa (gauge pressure) or less, and more preferably −0.06 MPa (gauge pressure) or less. Further, the lower limit of the pressure in the decompression removing step is usually −0.095 MPa (gauge pressure) or more. By setting the pressure in the storage tank 40 within the above range, it takes a long time to remove the organic solvent when the pressure is too high, or when the pressure is too low, the emulsion foams and the concentrator 60 or the like. It is possible to suppress or prevent emulsifiers from being mixed into the solvent. The pressure in the decompression removal step may be changed according to the progress of the decompression removal operation, and in the production method of the present invention, the pressure in the decompression removal step is lowered as the decompression removal operation progresses. This is preferable, and the time required for decompression removal can be further shortened.

Further, in the vacuum removing step of the production method of the present invention, the organic solvent is sprayed on the liquid surface of the emulsion stored in the storage tank 40 that has undergone the normal pressure removing step while spraying an aqueous solution of a defoaming agent. It is preferable to remove the emulsion under reduced pressure, which causes the emulsion to foam due to the reduced pressure, so that a part of the emulsion enters the concentrator 60 from the storage tank 40, resulting in a problem that the yield is lowered. It is possible to further improve the removal efficiency of the organic solvent while effectively preventing it.

As the aqueous solution of the defoaming agent used in the decompression removing step, the same method as in the above-mentioned normal pressure removing step can be used, and the spraying method and spraying conditions thereof are also the same as those in the above-mentioned normal pressure removing step. And similar conditions can be adopted. Further, in the vacuum removing step of the production method of the present invention, the type of the aqueous solution of the defoaming agent to be sprayed, the spraying method, and the spraying conditions may be the same as the above-mentioned normal pressure removing step, or at least a part thereof. May be different from the above-mentioned normal pressure removing step.

Further, in the vacuum removal step of the production method of the present invention, the temperature of the emulsion when the organic solvent contained in the emulsion is removed under reduced pressure in the storage tank 40 is the temperature of the organic solvent contained in the emulsion (that is, that is). , An organic solvent derived from a synthetic rubber solution or a dispersion) with respect to the boiling point Tb under atmospheric pressure, preferably controlled in the range of Tb-35 to Tb ± 0 ° C., and Tb-30 to Tb ±. It is more preferable to control the temperature in the range of 0 ° C., and further preferably to control the temperature in the range of Tb-25 to Tb-10 ° C.

Further, in the vacuum removing step of the production method of the present invention, the vacuum removing time when removing the organic solvent contained in the emulsion in the storage tank 40 under reduced pressure is preferably 1 to 20 hours, more preferably. 2 to 15 hours. In the production method of the present invention, in the above-mentioned normal pressure removing step, a part of the organic solvent contained immediately after emulsification of the emulsion obtained in the emulsifying step has already been removed. In addition, since the organic solvent is removed under reduced pressure in the vacuum removing step with a part of the organic solvent removed, even if the reduced pressure removal time is set to a relatively short time as described above, The organic solvent can be appropriately removed.

The vacuum removal of the organic solvent from the emulsion in the vacuum removal step is an operation of continuously obtaining an emulsion (that is, a mixing device of a synthetic rubber solution or dispersion and an emulsifier aqueous solution) in the emulsion step. The operation of continuously supplying the emulsion to the container 40 to obtain the emulsified liquid and continuously transferring the emulsion to the storage tank 40) may be completed, and then the emulsion may be started promptly, more specifically, continuously. After completing the operation of obtaining the emulsion, the operation may be started after performing various operations necessary for removing the organic solvent from the emulsion under reduced pressure in the vacuum removing step, but the operation of continuously obtaining the emulsion may be performed. After completion, the removal of the organic solvent from the emulsion at −0.005 to 0 MPa (gauge pressure) in the normal pressure removing step may be continued for a predetermined time, and then started.

As described above, according to the production method of the present invention, a latex of synthetic rubber can be obtained. The synthetic rubber latex thus obtained includes a pH adjuster, an antifoaming agent, a preservative, a chelating agent, an oxygen scavenger, a dispersant, an antiaging agent, etc., which are usually blended in the latex field. Additives may be blended.

Examples of the pH adjuster include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal hydrogen carbonates such as sodium hydrogen carbonate; ammonia. ; Organic amine compounds such as trimethylamine and triethanolamine; and the like; but alkali metal hydroxides or ammonia are preferable.

Further, if necessary, a concentration operation by centrifugation may be performed in order to increase the solid content concentration of the latex of the synthetic rubber.

The volume average particle size of the latex of the synthetic rubber produced by the production method of the present invention is preferably 0.1 to 10 μm, more preferably 0.5 to 3 μm, and further preferably 1 to 2 μm. By setting the volume average particle size in the above range, the latex viscosity becomes appropriate and it becomes easy to handle, and it is possible to suppress the formation of a film on the latex surface when the latex of synthetic rubber is stored.

The solid content concentration of the latex of the synthetic rubber produced by the production method of the present invention is preferably 30 to 70% by weight, more preferably 40 to 70% by weight. By setting the solid content concentration in the above range, it is possible to suppress the separation of the polymer particles when the latex of the synthetic rubber is stored, and also to suppress the aggregation of the polymer particles to generate coarse agglomerates. can.

The latex of the synthetic rubber of the present invention thus obtained can be made into a latex composition by blending various additives such as a cross-linking agent, and the latex composition can be a dip molded product or the like. In addition to being used to obtain a film molded product of No. 1, it can also be used for adhesives and the like.

Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples. In the following, "part" is based on weight unless otherwise specified. The tests and evaluations were as follows.

<Example 1>
(Preparation of cyclohexane solution (a) of synthetic polyisoprene)
Synthetic polyisoprene (trade name "NIPOL IR2200L", manufactured by ZEON Corporation) is mixed with cyclohexane (boiling point: 81 ° C) and dissolved by raising the temperature to 60 ° C with stirring to dissolve the synthetic polyisoprene concentration of 8% by weight. A cyclohexane solution (a) of synthetic polyisoprene was prepared.

(Preparation of aqueous emulsifier solution (b1))
An aqueous emulsifier solution (b1) having a potassium rosinate concentration of 1.2% by weight was prepared by mixing potassium rosinate as a fatty acid-based emulsifier with water at a temperature of 60 ° C.

(Manufacturing of synthetic polyisoprene latex)
Then, using the cyclohexane solution (a) and the emulsifier aqueous solution (b1) of the synthetic polyisoprene prepared above, the synthetic polyisoprene latex was produced using the emulsification apparatus shown in FIG.

Specifically, the cyclohexane solution (a) of the synthetic polyisoprene prepared above is stored in the polymer tank 10 in a state of being heated to 60 ° C., and is also prepared in the emulsifier tank 20 as described above. The emulsifier aqueous solution (b1) was stored in a heated state at 60 ° C., and these were stored in a line mixer as a premixer so that the weight ratio of "synthetic polyisoprene": "emulsifier" was 10: 1. By continuously supplying the emulsifying liquid to the mixing device 30 after premixing at It was continuously discharged to 40. As the mixing device 30, a homogenizer (trade name "Milder", manufactured by Pacific Kiko Co., Ltd.) was used.

Further, in this embodiment, by opening the valve 50, the storage tank 40 is opened, the pressure inside the storage tank 40 is kept at 0 MPa (gauge pressure), and the temperature of the emulsion is added to 80 ° C. The emulsion is transferred and stored in the storage tank 40 while continuously spraying a 0.1% by weight aqueous solution of a silicon-based defoaming agent (trade name "SM5512", manufactured by Dow Corning Co., Ltd.). Removal of cyclohexane in the tank 40 by evaporation (normal pressure removal) was performed at the same time. In this embodiment, as the storage tank 40, a storage tank 40 equipped with a spray device consisting of a pipe provided with a spray nozzle is used at one place above the storage tank 40, and a 0.1% by weight aqueous solution of a silicon-based defoaming agent is used. Was continuously sprayed from this spraying device to the entire surface of the emulsion transferred into the storage tank 40 at a pressure of 0.06 MPa. Further, in this example, the transfer speed of the emulsion to the storage tank 40 was set to 0.09 (1 / hr).

Then, in this embodiment, such transfer of the emulsion to the storage tank 40 and removal by evaporation of cyclohexane in the storage tank 40 (normal pressure removal) are performed on the emulsion discharged into the storage tank 40. After the amount was continuously increased to 76% by volume of the volume of the storage tank 40, the transfer of the emulsion to the storage tank 40 was stopped. Immediately after the transfer of the emulsion to the storage tank 40 was stopped, the amount of the emulsion in the storage tank 40 was 48% by volume of the volume of the storage tank 40 (the same applies to Examples 2 to 5). ). That is, it can be said that 28% by volume of cyclohexane was removed by removal by evaporation (removal of normal pressure) of cyclohexane.

Next, after stopping the transfer of the emulsion to the storage tank 40, a decompression pump is connected to the downstream side of the concentrator 60, and the emulsion in the storage tank 40 is heated to 80 ° C. in the storage tank. The decompression operation inside the 40 was started, and cyclohexane in the emulsion was removed under reduced pressure. In addition, also in the vacuum removal of cyclohexane, following the normal pressure removal described above, a 0.1% by weight aqueous solution of a silicon-based defoaming agent was sprayed from a spraying device provided at one place on the upper part of the storage tank 40. Cyclohexane was removed under reduced pressure while continuously spraying the entire surface of the emulsion at a pressure of 06 MPa. When removing the decompression, the decompression degree at the start is set to -0.02 MPa (gauge pressure), and the bubble surface height at the start of decompression (in this embodiment, 85% with respect to the total height inside the storage tank 40). The degree of decompression was gradually increased to −0.09 MPa (gauge pressure) so as to maintain the height). When removing cyclohexane under reduced pressure, the amount of cyclohexane recovered by the concentrator 60 was measured every hour, and the cyclohexane content in the emulsion was 100% by weight ppm or less with respect to the synthetic rubber in the emulsion. When it was determined that the pressure was reduced, the decompression removal was terminated (the same applies to Examples 1 to 5 and Comparative Examples 1 to 4 described later). In Example 1, the organic solvent removal time, which is the time from the start of mixing by the mixing device 30 to the end of decompression removal, was 14 hours. Further, in Example 1, the proportion of synthetic polyisoprene adhering to the wall surface of the storage tank 40 was 1.3% by weight, and the average particle size of the obtained synthetic polyisoprene latex was 1.09 μm.

<Example 2>
The concentration of the silicon-based defoaming agent is 0.009 weight as an aqueous solution of the silicon-based defoaming agent to be sprayed on the entire surface of the emulsion when the cyclohexane is removed under normal pressure and reduced pressure in the storage tank 40. % Was used, and the emulsification and removal of the organic solvent were carried out in the same manner as in Example 1 except that the spray pressure from the spraying device was 0.18 MPa. In Example 2, the foam surface height at the start of decompression was 80% of the total height inside the storage tank 40, so that the foam surface height was 80% when the decompression was removed. The degree of decompression was gradually increased from −0.02 MPa (gauge pressure) to −0.09 MPa (gauge pressure) so as to be maintained. In Example 2, the organic solvent removal time, which is the time from the start of mixing by the mixing device 30 to the end of decompression removal, was 13 hours. Further, in Example 2, the proportion of synthetic polyisoprene adhering to the wall surface of the storage tank 40 was 1.4% by weight, and the average particle size of the obtained synthetic polyisoprene latex was 1.12 μm.

<Example 3>
As the storage tank 40, one equipped with a spray device consisting of a pipe provided with a spray nozzle is used at four places on the upper part of the storage tank 40, and when the normal pressure removal and the reduced pressure removal of cyclohexane in the storage tank 40 are performed. As an aqueous solution of the silicon-based defoaming agent to be sprayed on the entire surface of the emulsion, a silicon-based defoaming agent having a concentration of 0.005% by weight is used, and the spray pressure from four spraying devices is used. The emulsion and the removal of the organic solvent were carried out in the same manner as in Example 1 except that the values were set to 0.16 MPa. In Example 3, the foam surface height at the start of decompression was 72% of the total height inside the storage tank 40, so that the foam surface height was 72% when the decompression was removed. The degree of decompression was gradually increased from −0.02 MPa (gauge pressure) to −0.09 MPa (gauge pressure) so as to be maintained. In Example 3, the organic solvent removal time, which is the time from the start of mixing by the mixing device 30 to the end of decompression removal, was 11 hours. Further, in Example 3, the proportion of synthetic polyisoprene adhering to the wall surface of the storage tank 40 was 1.1% by weight, and the average particle size of the obtained synthetic polyisoprene latex was 1.14 μm.

<Example 4>
When removing the cyclohexane under normal pressure and depressurizing in the storage tank 40, instead of the aqueous solution of the silicon-based defoaming agent, 0 of the mineral oil-based defoaming agent (trade name "SN Deformer 269, manufactured by Sannopco"). Emulsification and removal of the organic solvent were carried out in the same manner as in Example 1 except that an 08% by weight aqueous solution was used and the spray pressure from the spraying device was 0.07 MPa. Since the foam surface height at the start of depressurization was 79% of the total height inside the storage tank 40, the foam surface height should be maintained at 79% when decompressing is removed. , The degree of decompression was gradually increased from -0.02 MPa (gauge pressure) to -0.09 MPa (gauge pressure). In Example 4, from the start of mixing by the mixing device 30 to the end of decompression removal. The organic solvent removal time, which is the time, was 15 hours. In Example 4, the proportion of synthetic polyisoprene adhering to the wall surface of the storage tank 40 was 1.2% by weight, and the obtained synthetic poly was obtained. The average particle size of the isoprene latex was 1.12 μm.

<Example 5>
As the emulsifier aqueous solution, instead of the emulsifier aqueous solution (b1), potassium loginate as a fatty acid-based emulsifier has a concentration of 1% by weight, and sodium dodecylbenzenesulfonate as an alkylbenzene sulfonic acid-based emulsifier has a concentration of 0.5% by weight. In addition to using the emulsifier aqueous solution (b2) contained in the above, as the storage tank 40, a storage tank 40 equipped with a spray device consisting of a pipe provided with a spray nozzle at four locations above the storage tank 40 is used, and the storage tank 40 is used. A silicon-based defoaming agent having a concentration of 0.01% by weight as an aqueous solution of a silicon-based defoaming agent sprayed on the entire surface of the emulsion when the cyclohexane is removed under normal pressure and depressurized inside. Was used, and the emulsification and removal of the organic solvent were carried out in the same manner as in Example 1 except that the spray pressures from the four spraying devices were all 0.18 MPa. In Example 5, these were mixed so that the weight ratio of "synthetic polyisoprene": "emulsifier" was 10: 1 (the same applies to Comparative Examples 1 to 3 described later). Further, in Example 5, the foam surface height at the start of depressurization was 75% of the total height inside the storage tank 40, so that the foam surface height was 75% when the decompression was removed. The degree of decompression was gradually increased from −0.02 MPa (gauge pressure) to −0.09 MPa (gauge pressure) so as to be maintained. In Example 3, the organic solvent removal time, which is the time from the start of mixing by the mixing device 30 to the end of decompression removal, was 14 hours. Further, in Example 5, the proportion of synthetic polyisoprene adhering to the wall surface of the storage tank 40 was 0.7% by weight, and the average particle size of the obtained synthetic polyisoprene latex was 1.07 μm.

<Comparative Example 1>
As the aqueous solution of the emulsifier, the aqueous emulsifier (b2) was used instead of the aqueous emulsifier (b1), and the atmospheric pressure removal of cyclohexane in the storage tank 40 (that is, the emulsion was transferred to the storage tank 40). The pressure inside the storage tank 40 was set to -0.02 MPa (gauge pressure) when the cyclohexane was removed during the period, and the entire surface of the emulsion was covered when the normal pressure was removed and the pressure was removed under reduced pressure. As the aqueous solution of the silicon-based defoaming agent to be sprayed, the solution was carried out except that the concentration of the silicon-based defoaming agent was 0.09% by weight and the spray pressure from the spraying device was 0.18 MPa. Emulsification and removal of the organic solvent were carried out in the same manner as in Example 1. In Comparative Example 1, since a part of the emulsified liquid entered the concentrator 60 from the storage tank 40 during the transfer of the emulsified liquid, the emulsification and removal operations of the organic solvent were performed a plurality of times. Since it became necessary to interrupt the process, the organic solvent removal time, which is the time from the start of mixing by the mixing device 30 to the end of the vacuum removal, was as long as 26 hours. Further, in Comparative Example 1, after the transfer of the emulsion was completed, when the emulsion was removed under reduced pressure, the foam surface height was maintained at about 85% from -0.02 MPa (gauge pressure) to -0.09 MPa (gauge). The degree of decompression was gradually increased to pressure). In Comparative Example 1, the proportion of synthetic polyisoprene adhering to the wall surface of the storage tank 40 was 3.2% by weight, and the average particle size of the obtained synthetic polyisoprene latex was 1.15 μm.

<Comparative Example 2>
In the normal pressure removal of cyclohexane in the storage tank 40, the aqueous solution of the silicon-based defoaming agent was not sprayed, and in the decompression removal of the cyclohexane in the storage tank 40, the aqueous solution of the silicon-based defoaming agent. The spray was not continuous spray but timely spray (spray only when the liquid level rises), and the aqueous solution of the silicon defoamer with a concentration of 0.09% by weight of the silicon defoamer was used. Emulsification and removal of the organic solvent were carried out in the same manner as in Example 5 except that the spray pressure was 0.18 MPa in each of the four spraying devices. In Comparative Example 2, the foam surface height at the start of depressurization was 92% of the total height inside the storage tank 40, so that the foam surface height was 92% when the decompression was removed. The degree of decompression was gradually increased from −0.02 MPa (gauge pressure) to −0.09 MPa (gauge pressure) so as to be maintained. In Comparative Example 2, the organic solvent removal time, which is the time from the start of mixing by the mixing device 30 to the end of decompression removal, was 18 hours. Further, in Comparative Example 2, the proportion of synthetic polyisoprene adhering to the wall surface of the storage tank 40 was 2.4% by weight, and the average particle size of the obtained synthetic polyisoprene latex was 1.25 μm.

<Comparative Example 3>
In the normal pressure removal of cyclohexane in the storage tank 40, the aqueous solution of the silicon-based defoaming agent was not sprayed, and as the storage tank 40, a pipe-shaped nozzle with an inner diameter of about 1 cmφ was placed in one place on the upper part of the storage tank 40. The emulsification and removal of the organic solvent were carried out in the same manner as in Example 1 except that the one provided with the supply device consisting of the above was used and the supply pressure of the aqueous solution of the silicon-based defoaming agent was set to 0.01 MPa. rice field. In Comparative Example 3, when the decompression degree was set to −0.02 MPa (gauge pressure) during the decompression removal operation, a part of the emulsified liquid entered the concentrator 60 from the storage tank 40. Therefore, since it became necessary to interrupt the decompression removal operation a plurality of times, the organic solvent removal time, which is the time from the start of mixing by the mixing device 30 to the end of decompression removal, is as long as 22 hours. became. Further, in Comparative Example 3, even if the decompression degree was set to −0.02 MPa (gauge pressure) when removing the decompression, the foam surface height was about 85% after the emulsion did not enter the concentrator 60. The degree of decompression was gradually increased from −0.02 MPa (gauge pressure) to −0.09 MPa (gauge pressure) so as to be maintained at. In Comparative Example 3, the proportion of synthetic polyisoprene adhering to the wall surface of the storage tank 40 was 3.9% by weight, and the average particle size of the obtained synthetic polyisoprene latex was 1.33 μm.

<Comparative Example 4>
As the storage tank 40, one equipped with a supply device consisting of a pipe-shaped nozzle having an inner diameter of about 1 cmφ is used at one place on the upper part of the storage tank 40, and cyclohexane is removed under normal pressure and reduced pressure in the storage tank 40. At that time, emulsification and removal of the organic solvent were carried out in the same manner as in Example 1 except that the supply pressure of the aqueous solution of the silicon-based defoaming agent was 0.01 MPa. In Comparative Example 4, the foam surface height at the start of decompression was 90% of the total height inside the storage tank 40, so that the foam surface height was 90% when the decompression was removed. The degree of decompression was gradually increased from −0.02 MPa (gauge pressure) to −0.09 MPa (gauge pressure) so as to be maintained. In Comparative Example 4, the organic solvent removal time, which is the time from the start of mixing by the mixing device 30 to the end of decompression removal, was 17 hours. Further, in Comparative Example 4, the proportion of synthetic polyisoprene adhering to the wall surface of the storage tank 40 was 2.8% by weight, and the average particle size of the obtained synthetic polyisoprene latex was 1.14 μm.

As shown in Table 1, the emulsion continuously obtained by the mixing device 30 is continuously transferred into the tank 40 adjusted to the pressure condition of −0.005 to 0 MPa with a gauge pressure, while being continuously transferred to the tank. When the normal pressure removal of the organic solvent in 40 is performed, the organic solvent is removed while spraying the aqueous solution of the defoaming agent on the liquid surface of the emulsion transferred into the tank 40. It was possible to shorten the organic solvent removal time while suppressing the adhesion of synthetic polyisoprene to the wall surface of the tank 40 to a small extent, and therefore, it was possible to manufacture in a short time while achieving a high yield (Example). 1-5).

On the other hand, when the emulsified liquid continuously obtained by the mixing device 30 is continuously transferred into the tank 40 and the pressure condition in the tank 40 is set to −0.02 MPa in gauge pressure, A part of the emulsion enters the concentrator 60 from the storage tank 40 (maximum foam surface height exceeds 100%), resulting in a long organic solvent removal time, and further, synthetic polyisoprene. As a result, the adhesion to the wall surface of the tank 40 also increased (Comparative Example 1).
Further, the emulsion continuously obtained by the mixing device 30 was continuously transferred to the tank 40 adjusted to the pressure condition of −0.005 to 0 MPa with a gauge pressure, but at this time, the defoaming agent was used. When the above was not added, the synthetic polyisoprene adhered to the wall surface of the tank 40 more, and the organic solvent removal time became longer (Comparative Examples 2 and 3).
Further, when the emulsion continuously obtained by the mixing device 30 is continuously transferred into the tank 40 adjusted to the pressure condition of −0.005 to 0 MPa with a gauge pressure, an antifoaming agent is added. However, when the defoaming agent was not added by spraying, the synthetic polyisoprene adhered more to the wall surface of the tank 40, and the organic solvent removal time became longer. (Comparative Example 4).

Claims (6)

An emulsification step in which an emulsified solution is continuously obtained by continuously supplying and mixing a solution or dispersion of synthetic rubber in which synthetic rubber is dissolved or dispersed in an organic solvent and an aqueous solution of an emulsifier to a mixing device. When,
The organic solvent is usually removed in the container while continuously transferring the emulsified liquid continuously obtained in the emulsification step into a container adjusted to a pressure condition of −0.005 to 0 MPa with a gauge pressure. Equipped with a pressure relief process,
A method for producing a synthetic rubber latex, which removes an organic solvent while spraying an aqueous solution of an antifoaming agent on the liquid surface of an emulsion transferred into the container in the normal pressure removing step. Further, a vacuum removal step of removing the organic solvent under a reduced pressure condition of −0.01 MPa or less at a gauge pressure while spraying an aqueous solution of a defoaming agent on the liquid surface of the emulsion that has undergone the normal pressure removing step is further performed. The method for producing a latex of synthetic rubber according to claim 1. The method for producing a latex of synthetic rubber according to claim 1 or 2, wherein the aqueous solution of the defoaming agent has a concentration of the defoaming agent of 0.005 to 0.1% by weight. The method for producing a latex of synthetic rubber according to any one of claims 1 to 3, wherein an aqueous solution of the defoaming agent containing a silicon-based defoaming agent is used. Claim 1 in the normal pressure removing step, the organic solvent is removed while controlling the temperature of the emulsion in the temperature range of Tb-10 to Tb + 5 ° C. with respect to the boiling point Tb of the organic solvent under atmospheric pressure. The method for producing a latex of synthetic rubber according to any one of 4 to 4. The method for producing a latex of synthetic rubber according to any one of claims 1 to 5, wherein an aqueous solution of the emulsifier containing a fatty acid salt and / or an alkylbenzene sulfonate is used.

Images