JP2000297108A - Manufacture of rubber latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highly concentrated rubber latex having a small diameter suitable as a material for ABS resin effectively in a relatively short time without generation of agglomerates by polymerizing an aliphatic conjugated diene in a state of emulsion while adding an polymerization initiator continuously or intermittently for a predetermined time. SOLUTION: An aliphatic conjugated diene or a mixture of an aliphatic conjugated diene and a vinyl-based monomer is polymerized by adding an polymerization initiator continuously or intermittently in 2 to 30 minutes. The initiator to be used is preferably persulfate only or a redox initiator of a combination of an organic hydrogen peroxide, an iron ion and formaldhyde sulfoxylate. The material to be added in 2 to 30 minutes means a material which satisfies the last requirement for initiation of polymerization, for example, if the initiator is a thermally decomposable compound, such a material means the compound itself and if the initiator is a redox catalyst and a catalyst and a reducing agent already exist in a reaction vessel, it means the last component, that is, an organic hydrogen peroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rubber latex having a high concentration and a small particle diameter, which is suitable for a raw material of an ABS resin, in a relatively short time, efficiently and without the generation of aggregates.

[0002]

2. Description of the Related Art ABS resins are mainly obtained by graft copolymerization of an aromatic vinyl monomer and a vinyl cyanide monomer onto rubbery polymer particles by an emulsion polymerization method. Is a thermoplastic resin composition having a form in which rubbery polymer particles are finely dispersed in a copolymer of a monomer and a vinyl cyanide-based monomer, and has excellent moldability, mechanical strength, and chemical resistance. Therefore, it is used in a wide range of application fields.

It is well known that the properties of the ABS resin largely depend on the form of dispersion of the rubbery polymer particles constituting the ABS resin. For example, the impact resistance is superior as the particle size of the rubbery polymer is larger, and conversely, the smoothness of the resin surface is smaller.

[0004] Such rubbery polymer particles are generally
It is often supplied in advance in the form of rubber latex by emulsion polymerization. It is generally known that the particle size of the rubber latex obtained by the emulsion polymerization is controlled by increasing or decreasing the polymerization reaction rate, the amount of the emulsifier, the number of polymer particles, and the like during the polymerization.

[0005] In the case of ABS resin, generally 200 to 400 n
Rubber latex having a particle size of m is preferably used. However, in order to obtain a rubber latex having a particle diameter suitable for an ABS resin in this range, a very long polymerization time is required, and it is not possible to obtain a production amount per unit time, which means that the production efficiency is excellent. I could not say.

Accordingly, as a method for more efficiently obtaining a rubber latex having a desired particle size, Japanese Patent Application Laid-Open No. 56-16770 is disclosed.
No. 4, JP-A-59-93701, Japanese Patent Publication No.
Japanese Patent No. 79366 proposes a method called "enlargement" in which small rubber latexes of about 50 to 150 nm are produced in advance, and then they are aggregated and controlled to a desired particle diameter.

[0007] In order to improve the production efficiency of rubber latex as a raw material of the ABS resin, it is common practice to shorten the polymerization time or increase the throughput of the production equipment.

However, when the polymerization rate is increased to improve the production efficiency of the small particle rubber latex, the viscosity of the rubber latex increases remarkably, and the aliphatic conjugated diene used for producing the rubber latex for ABS resin of the present invention is used. Since the polymerization of the system monomer is an exothermic reaction, the temperature of the polymerization vessel may be remarkably increased due to insufficient heat removal of the polymerization vessel, and in some cases, a serious disaster may occur. In order to avoid such a situation, it is possible to reduce the viscosity of the rubber latex and increase the heat removal efficiency by adding an electrolyte or a water-soluble substance.
The quality of the S resin product is adversely affected, and the generation of aggregates during the production of rubber latex becomes remarkable.

Also, when the productivity is improved by increasing the concentration of the rubber latex, the viscosity also increases significantly.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to provide an AB
In order to produce small particle rubber latex suitable for S resin with excellent efficiency, a method for producing rubber latex with high solid content in a short time with almost no induction period and with extremely small generation of aggregates is provided. Is to do.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber latex for an ABS resin which solves the above-mentioned problems and has excellent productivity.

The gist of the present invention is to provide a rubber composition by emulsion polymerization of an aliphatic conjugated diene monomer or a monomer mixture comprising an aliphatic conjugated diene monomer and a vinyl monomer copolymerizable therewith. In the method for producing a latex, a method for producing a rubber latex is characterized in that polymerization is initiated by adding a polymerization initiator over a period of 2 to 30 minutes.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

As the aliphatic conjugated diene monomer used for producing the rubber latex of the present invention, 1,3-butadiene, isoprene, chloroprene and the like can be used.
-Butadiene is preferred.

Other copolymerizable monomers include aromatic vinyl monomers, vinyl cyanide monomers, (meth)
One or two or more selected from the group consisting of acrylic esters can be used. Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, p-chlorostyrene, p-methylstyrene and the like, and styrene and α-methylstyrene are particularly preferred. Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, ethacrylonitrile, maleonitrile, fumaronitrile and the like, and acrylonitrile is particularly preferred. Examples of (meth) acrylates include methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, and particularly n-
Butyl acrylate and 2-ethylhexyl acrylate are preferred. These can be used alone or in combination of two or more even in the same group.

The amount of the aliphatic conjugated diene monomer in the monomer mixture is 30 to 100 parts by weight, and the amount of the monomer copolymerizable therewith is 0 to 70 parts by weight. The body is 40 to 90 parts by weight and 10 to 60 parts by weight of other copolymerizable monomers. If the proportion of the aliphatic conjugated diene-based monomer is less than 30 parts by weight, the inherent performance of the ABS resin cannot be exhibited.

Examples of the emulsifier used in the emulsion polymerization include disproportionated rosin acid, alkali metal salts of higher fatty acids such as oleic acid and stearic acid, alkali metal salts of sulfonic acids such as dodecylbenzenesulfonic acid and lauryl sulfate, and alkenylsuccinic acid. Alkali metal salts of dibasic acids and the like can be used alone or in combination of two or more.

The amount of the emulsifier used is 0.2 to 10.0 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the monomer or the monomer mixture.

The polymerization initiator used in the present invention can be roughly classified into two types, one using a thermally decomposable initiator represented by a "hot rubber" formulation, and one represented by a "cold rubber" formulation. It is a redox-based initiator that utilizes an oxidation-reduction reaction.

Examples of the thermally decomposable initiator include persulfates such as potassium persulfate and ammonium persulfate, 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), Azo compounds such as 2,2′-azobis (2-methyl-butyronitrile),
Diacyl peroxides such as benzoyl peroxide and lauroyl peroxide; dialkyl peroxides such as dicumyl peroxide, t-butylcumyl peroxide and di-t-butyl peroxide; t-
Organic peroxides such as peroxyesters such as butylperoxyacetate can be used alone or in combination of two or more.

The redox initiator comprises a combination of a polymerization initiator, a catalyst and a reducing agent. As the polymerization initiator, organic hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide and the above-mentioned persulfates are used.

As the catalyst, a combination of metal ions such as iron, copper, and cobalt, and a pyrophosphate or ethylenediaminetetraacetate as a stabilizer thereof is used.

As the reducing agent, reducing sugars such as formaldehyde sulfoxylate salt (Rongalit) and dextrose, and reducing inorganic salts such as sulfites and thiosulfates are used.

Preferred polymerization initiators include persulfate alone, organic hydroperoxide and iron ion,
It is a redox polymerization initiator combined with a formaldehyde sulfoxylate salt.

In addition to these polymerization initiators, it is also possible to use alkaline substances such as sodium hydroxide, potassium hydroxide and aqueous ammonia as pH adjusters, and sodium sulfate, potassium chloride and sodium phosphate as viscosity reducing agents. it can.

There are no particular restrictions on the amounts of these polymerization initiators and other additives used. However, if the total electrolytic mass is too large, polymer aggregates are likely to be generated. In particular, the amount of the viscosity reducing agent used should be reduced in terms of aggregates.

In order to achieve the object of the present invention, it is necessary to control the method of adding the above-mentioned thermally decomposable initiator or redox polymerization initiator (initiator-catalyst-reducing agent). Specifically, the polymerization is initiated by adding these polymerization initiators continuously or intermittently over a period of 2 to 30 minutes. The substance which needs to be added over a period of 2 to 30 minutes as referred to herein means a substance which satisfies the last requirement necessary for the initiation of polymerization. For example, a thermally decomposable initiator means itself. If the catalyst and the reducing agent among the redox initiators are already present in the reactor, it indicates the last organic hydroperoxide. Preferably, it is 5 to 20 minutes. Among them, the addition method thereof may be either continuous addition or intermittent addition of several parts. In this case, the time from the start of the addition to the end of the entire addition may be within a predetermined range. However, it is not preferable that the supply amount fluctuates greatly per unit time between the initial period and the latter period since the object of the present invention cannot be achieved.

These additions are carried out when the temperature in the polymerization vessel is 20 to
It is preferably done at 80 ° C. More preferably, it is 30 to 70 ° C. Even if added below 20 ° C. or above 80 ° C., the viscosity of the latex may increase.

In view of the purpose of increasing the production efficiency of the rubber latex, the time required for the polymerization is 15 hours or less, preferably 12 hours. Means the time until the polymerization rate is achieved.

In the emulsion polymerization, a so-called “induction period” may occur during an interval between the time when a predetermined polymerization initiator is added and the time when the polymerization actually starts, and this may occur from the viewpoint of production efficiency. It is not desirable for a lag phase to occur,
It is preferable to set the time to 15 minutes or less.

The solid content of the obtained rubber latex is 25 to 55% by weight, preferably 30 to 50% by weight in view of the above-mentioned conflicting phenomena of the productivity and the increase in viscosity resulting in a decrease in heat removal efficiency. . If it is less than 25% by weight, the original excellent productivity cannot be obtained because it is too thin, and if it exceeds 55% by weight, the viscosity is remarkably increased.

The upper limit of the viscosity of the rubber latex naturally depends on the scale and structure of the apparatus, but is generally less than 1.0 Pa · s, preferably less than 0.5 Pa · s. 1.0Pa ・
When the value exceeds s, the stirring efficiency is deteriorated, and significant heat removal failure occurs, which may hinder production.

The particle size of the rubber latex is from 50 to 150 nm, preferably from 60 to 130 nm, as a weight average particle size, since the particle size of the rubber latex is adjusted to a particle size suitable for the ABS resin by an enlarging operation later. If it is less than 50 nm,
If the viscosity of the rubber latex is significantly increased, and if it exceeds 150 nm, the polymerization time is prolonged, and the efficiency of enlargement may be further deteriorated.

As described above, the obtained rubber latex has a weight average particle diameter of 200 to 400 nm by an enlargement treatment for increasing the particle diameter, and is used as a raw material for ABS resin.

The method of the enlargement treatment is not particularly limited, but a method of adding an acidic substance or an electrolyte, a specific organic solvent, a copolymer latex containing an acid group, or a method of freezing, sharpening, or applying pressure to the latex. A method of destabilizing can be used.

Further, an aromatic vinyl monomer, a vinyl cyanide monomer, or another copolymerizable monomer is graft-copolymerized with the enlarged rubber latex, The desired ABS resin can be produced.

[0037]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited by these examples. In the examples, "parts,%" means "parts by weight,% by weight" unless otherwise specified. In the following Examples and Comparative Examples, measurement and items of various physical properties were as follows. It was measured by the method.

Measurement of solid content; latex in aluminum dish 2
It was precisely weighed to about g, dried in an oven at 180 ° C. for 30 minutes, and determined from the weight after drying.

Particle size of rubber latex: The size of 300 to 400 solid rubber-like polymer particles was counted using a transmission electron microscope, and the weight average particle size was determined.

Latex viscosity: B manufactured by Tokyo Keiki Co., Ltd.
The measurement was performed at a latex temperature of 25 ° C. using a shape viscosity meter BL type.

Induction period: 10 from the start of polymerization initiator addition
A sample was taken every minute to determine the time until the formation of the polymer was recognized.

Determination of Polymerization Time and Termination of Polymerization: Samples were taken every 30 minutes after the formation of the polymer was recognized, and the polymerization was terminated when the polymerization conversion reached 97% or more. The polymerization time was the time required from the generation of the polymer was observed to the end of the polymerization.

The amount of aggregates: The latex after polymerization was filtered with a gauze, the generated aggregates were washed with water and dried, and the ratio to the charged monomers was determined by weight ratio.

Example 1 The following substances were placed in a 50-liter pressure vessel equipped with a stirrer and a warm water jacket for temperature control.

Deionized water (hereinafter simply referred to as water) 145 parts Potassium rosinate 2.0 parts Sodium oleate 1.0 parts Sodium hydroxide 0.001 parts Sodium sulfate 0.20 parts Sodium formaldehyde sulfoxylate Hydrate 0.20 part Styrene monomer 1.5 part Diisopropylbenzene hydroperoxide 0.20 part t-dodecyl mercaptan 0.15 part After charging with nitrogen and 18.5 parts of 1,3-butadiene, 50 The temperature was raised to ° C. Next, a catalyst aqueous solution comprising 0.20 parts of anhydrous sodium pyrophosphate, 0.0100 parts of ferrous sulfate heptahydrate, and 5.0 parts of water was continuously added over 5 minutes to start polymerization. The induction period at this time was within 10 minutes (1
The generation of polymer was already observed in the 0 minute sample). After the polymerization was started, the temperature was raised to 60 ° C. in 30 minutes, and then a mixture consisting of 74.0 parts of 1,3-butadiene and 6.0 parts of styrene was continuously supplied into the reactor over 180 minutes.

After 8 hours, the remaining 1,3-butadiene monomer was removed by stripping, and the solid content was 40.2%.
%, The weight average particle diameter is 74 nm, and the viscosity is 0.066 Pa ·
s rubber latex was obtained. The amount of aggregate generated is 0.0
8%.

Example 2 Polymerization was carried out in the same manner as in Example 1 except that the time required for adding the aqueous catalyst solution was changed to 24 minutes. The induction period was within 10 minutes, the polymerization time was 9 hours, and the solid content was not changed. A rubber latex having 40.0%, a weight average particle diameter of 88 nm and a viscosity of 0.040 Pa · s was obtained. The generated aggregate was 0.11%.

Example 3 In the same polymerization as in Example 1, anhydrous sodium pyrophosphate and ferrous sulfate heptahydrate were charged in a reactor in advance, while sodium formaldehyde sulfoxylate dihydrate used was used. An aqueous solution of a reducing agent consisting of a product (equal amount) and water (5 parts) was added continuously over 5 minutes to initiate polymerization. Induction period within 10 minutes, polymerization time 8 hours, solids 40.5%, weight average particle size 75n
m, a rubber latex having a viscosity of 0.062 Pa · s was obtained. The generated aggregate was 0.09%.

Example 4 In the same polymerization as in Example 1, anhydrous sodium pyrophosphate and ferrous sulfate heptahydrate were charged in a reactor in advance, and diisopropylbenzene hydroperoxide (equal amount) was used. ) Is divided into 5
Each was added every 2 minutes to initiate polymerization. A rubber latex having an induction period of 10 minutes or less, a polymerization time of 8 hours, a solid content of 40.1%, a weight average particle diameter of 78 nm, and a viscosity of 0.055 Pa · s was obtained. The generated aggregate was 0.07%.

Example 5 The following substances were charged into a 50-liter pressure-resistant container equipped with a stirrer and a warm water jacket for temperature control.

Deionized water 145 parts Dipotassium alkenyl succinate 0.6 parts Potassium oleate 1.4 parts N-butyl acrylate 10.0 parts Diisopropylbenzene hydroperoxide 0.20 parts t-dodecyl mercaptan 0.25 parts And then replaced with nitrogen, 10.0 parts of 1,3-butadiene was charged, and the temperature was raised to 45 ° C. Then, an aqueous solution comprising 0.001 part of disodium ethylenediaminetetraacetate 0.001 part of ferrous sulfate heptahydrate 0.0003 part of sodium formaldehyde sulfoxylate dihydrate 0.15 part of water and 5.0 parts of water was continuously fed for 8 minutes. Was added to initiate polymerization. The induction period at this time was within 10 minutes (the generation of polymer was already observed in the 10-minute sample). After the polymerization was started, the temperature was raised to 55 ° C. in 30 minutes, and then a mixture of 40.0 parts of 1,3-butadiene and 40.0 parts of n-butyl acrylate was continuously introduced into the reactor over 120 minutes. Supplied.

After 8 hours, the remaining 1,3-butadiene monomer was removed by stripping, and the solid content was reduced to 40.0%.
%, The weight average particle diameter is 69 nm, and the viscosity is 0.085 Pa ·
s rubber latex was obtained. The amount of aggregate generated is 0.1
2%.

Example 6 The following substances were placed in a 50-liter pressure vessel equipped with a stirrer and a warm water jacket for temperature control.

Deionized water 120 parts Potassium rosinate 1.0 part Sodium oleate 1.0 part Trisodium phosphate 0.50 parts Acrylonitrile 5.0 parts t-Dodecyl mercaptan 0.20 parts 95 parts of 1,3-butadiene was charged and the temperature was raised to 65 ° C. Next, an initiator aqueous solution consisting of 0.20 parts of potassium persulfate and 5.0 parts of water was continuously added over 10 minutes to start polymerization. The induction period at this time was within 10 minutes. After the polymerization was started, the temperature was raised to 75 ° C. in 60 minutes, and after 10 hours, the remaining 1,3-butadiene monomer was removed by stripping. The solid content was 44.5%, the weight average particle diameter was 92 nm, A rubber latex having a viscosity of 0.145 Pa · s was obtained. The amount of generated aggregates was 0.25%.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that the time required for adding the aqueous catalyst solution was changed to 0.5 minute. The induction period was within 10 minutes, and the polymerization time was 8 hours. A viscous rubber latex having a solid content of 40.3%, a weight average particle diameter of 47 nm, and a viscosity of 1.22 Pa · s was obtained.
The generated aggregate was 0.10%.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that the time required for adding the aqueous catalyst solution was changed to 45 minutes. The induction period was 20 to 30 minutes, and the polymerization time was 1 minute.
It became 6 hours, and a rubber latex having a solid content of 40.0%, a weight average particle diameter of 105 nm, and a viscosity of 0.022 Pa · s was obtained. The generated aggregate was 0.15%.

Comparative Example 3 Polymerization was carried out in the same manner as in Example 1, except that the amount of sodium sulfate used was changed to 1.2 parts and the time required for adding the aqueous catalyst solution was changed to 0.5 minutes. A rubber latex having an induction period of 10 minutes or less, a polymerization time of 8 hours, a solid content of 40.1%, a weight average particle diameter of 55 nm and a viscosity of 0.080 Pa · s was obtained. The generated aggregate was as large as 2.52%.

Comparative Example 4 Polymerization was carried out in the same manner as in Example 1 except that the aqueous catalyst solution was previously charged before the temperature was raised. The induction period was within 10 (from 50 ° C.), and the polymerization time was 8 hours. Time, solids content 40.1%, weight average particle size 48n
m, a viscous rubber latex having a viscosity of 1.02 Pa · s was obtained. The generated aggregate was 0.16%.

Comparative Example 5 The same procedure as in Example 1 was performed except that the amount of iron sulfate heptahydrate used was changed to 0.0010 parts and the time required for adding the catalyst aqueous solution was changed to 0.5 minutes. A rubber latex having an induction period of 40 minutes to 50 minutes, a polymerization time of 18 hours, a solid content of 40.1%, a weight average particle diameter of 96 nm, and a viscosity of 0.046 Pa · s was obtained. The generated aggregate was 0.19%.

As is clear from the above, the rubber latex obtained by the production method of this example has a sufficiently high solid content and a low viscosity. The time required for the production is short, and the amount of generated aggregates is small.

On the other hand, in Comparative Example 1 in which the catalyst was added in a short time, the viscosity of the latex was significantly increased, while in Comparative Example 2 in which the addition was long, the polymerization time was long.
Further, in Comparative Example 3 in which a large amount of electrolyte was used to avoid an increase in viscosity, a large amount of agglomerates was generated, and even in Comparative Example 4 in which the addition method did not satisfy the requirements of the present invention, the viscosity of the latex was significantly increased. Further, when the viscosity of the rubber latex is reduced by reducing the amount of the catalyst, the induction period becomes significantly longer, and the polymerization time also becomes longer.

[0062]

According to the method of the present invention, a low-viscosity rubber latex can be obtained in a short time, and the amount of monomers that can be polymerized in a reactor can be increased.
It is economically advantageous in the production of BS resin.

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Claims (3)

[Claims] 1. A rubber latex is produced by emulsion polymerization of an aliphatic conjugated diene monomer or a monomer mixture comprising an aliphatic conjugated diene monomer and a vinyl monomer copolymerizable therewith. A method for producing a rubber latex, wherein polymerization is initiated by continuously or intermittently adding a polymerization initiator over a period of 2 to 30 minutes. 2. A rubber latex is produced by emulsion polymerization of an aliphatic conjugated diene monomer or a monomer mixture comprising an aliphatic conjugated diene monomer and a vinyl monomer copolymerizable therewith. In the method, a rubber latex characterized in that polymerization is initiated by adding at least one polymerization initiator selected from persulfates, azo compounds and organic peroxides over a period of 2 to 30 minutes. Production method. 3. A rubber latex is prepared by emulsion polymerization of an aliphatic conjugated diene monomer or a monomer mixture comprising an aliphatic conjugated diene monomer and a vinyl monomer copolymerizable therewith. In the method for producing using a redox polymerization initiator consisting of an oxide initiator, a catalyst and a reducing agent, at least one selected from an organic peroxide initiator, a catalyst and a reducing agent is treated for a time of 2 to 30 minutes. A method for producing rubber latex, wherein polymerization is initiated by adding over a period of time.