JPH0848717A - Recovery method of polymer - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a method for recovering a polymer from a polymer latex, which contains less fine powder particles and has excellent powder characteristics. [Structure] A method for recovering a polymer, which comprises coagulating a polymer latex under a specific pretreatment method, a specific coagulant concentration and a specific stirring condition.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for recovering a polymer from a polymer latex obtained by emulsion polymerization,
More specifically, the present invention relates to a method for coagulating a polymer which can be controlled to an arbitrary particle size, has few fine powder particles, and has excellent powder characteristics.

2. Description of the Related Art Generally, in order to recover a powdery polymer from a polymer latex produced by emulsion polymerization, it is necessary to add a coagulating agent to the polymer latex to coagulate the polymer latex. As the most general method for coagulating such a polymer latex, a method is known in which the polymer latex and a coagulant are continuously supplied to a coagulation tank to cause coagulation and aggregation. However, this method has a problem that fine powder is generated. For example, there are many fine powders, there is a risk of dust explosion, there is a risk of fire explosion due to deterioration of carbonization resistance, there is a problem of environmental deterioration due to dusting, etc. There is a problem in that As a second method, a method is known in which the polymer latex is fed to a twin-screw extruder having a dehydration slit together with a coagulant (Japanese Patent Publication No. 59-37021). However, this method has a problem in that the recovered polymer cannot be sufficiently washed with water, so that the soap and the coagulant remain in the final product, thereby deteriorating the quality of the polymer. As a third method, there is a method in which a coagulant is sprayed into the coagulation chamber in the form of gas or mist and brought into contact with droplets of the polymer latex in space to coagulate.
(JP-A-58-87102). However, in this method, it is necessary to coagulate the latex in the gas phase within a short time in which the latex droplets fall to a sufficient hardness. There is a problem that a high coagulation device is required and the equipment cost increases. In addition, latex particles collide with the wall surface due to the drift of the gas in the tower during spraying, and are easily attached, or the coagulated particles fall into the aqueous phase and the coagulated particles are broken by the impact when colliding,
Since fine powders are easily generated, it is difficult to obtain coagulated particles of 300 μm or more. A fourth method is a method of slowly coagulating the polymer latex (Japanese Patent Publication No. 3-51728). However, in this method, since the concentration of the coagulant is low, the inside of the coagulated particles is not fully coagulated, and as a result, the water content of the coagulated particles is high and only bulk density is low.

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned prior art, and it is possible to select polymer particles containing few fine powders, easy to handle, excellent in productivity, and excellent in powder characteristics. The purpose of the present invention is to provide a method for coagulating a polymer latex that can be recovered by controlling the particle size of the polymer latex.

[0002]

Means and Action for Solving the Problems The present inventors have
As a result of intensive studies to solve the above-mentioned problems, the pretreatment method of the polymer latex in the coagulation step, the coagulant concentration, the coagulation temperature and the stirring conditions are limited, so that the solution of the problems can be achieved. They have found and arrived at the present invention. That is, in the present invention, when coagulating the polymer latex, 0.3 × (coagulation value) ≦
Coagulant concentration in the latex (mmol / L) ≤ 0.9 x (coagulation value) is added to and mixed with the polymer latex, and the coagulation value is more than the coagulation value of this polymer latex. The present invention provides a method for recovering a polymer, which is characterized in that it is coagulated at an agent concentration.

Further, the present invention comprises coagulating a polymer latex comprising a vinyl polymer and / or a rubber-modified vinyl polymer and having a rubber-like polymer content of 0 to less than 60% by weight. A coagulant having a deposition value or less is added to and mixed with the polymer latex, and the polymer latex is coagulated under the following conditions (a), (b) and (c), and then under the condition (d). A method for recovering a polymer by heat treatment. (A) Coagulation temperature (° C) Tv-20 <Coagulation temperature <Tv + 30 where Tv; Vicat softening point of polymer to be recovered (b) Coagulant concentration The coagulant is a salt and the cation of the coagulant is When monovalent C ≦ coagulant concentration (mmol / L) ≦ C + 2000, when coagulant is a salt and cation of the coagulant is divalent C ≦ coagulant concentration (mmol / L) ≦ C + 30, coagulation When the agent is a salt and the cation of the coagulant is trivalent, C ≦ coagulant concentration (mmol / L) ≦ C + 10 When the coagulant is acid C ≦ coagulant concentration (mmol / L) ≦ C + 30 C: Coagulation value (mmol / l) (C) The polymer latex and the coagulant are contacted with stirring, and the peripheral speed of the tip of the stirring blade is 10 ≦ the peripheral speed of the stirring blade ≦ 500 (cm / s) ( D) Heat treatment condition Tv ≦ treatment temperature (° C.) ≦ Tv + 50 is provided.

The present invention also provides a method of coagulating a polymer latex comprising a rubber-modified vinyl polymer and having a rubber-like polymer content of 60% by weight or more, in which a coagulant having a coagulation value or less is previously added to the polymer latex. A method for recovering a polymer, in which the polymer latex is added and mixed with, and the polymer latex is coagulated under the following conditions (e), (f) and (g) and then heat-treated under the condition (h). (E) Coagulation temperature (° C) Tv-40 <Coagulation temperature <Tv + 20 where Tv; Vicat softening point of polymer to be recovered (F) Coagulant concentration The coagulant is a salt and the cation of the coagulant is When monovalent C ≦ coagulant concentration (mmol / L) ≦ C + 2000, when coagulant is a salt and cation of the coagulant is divalent C ≦ coagulant concentration (mmol / L) ≦ C + 30, coagulation When the agent is a salt and the cation of the coagulant is trivalent, C ≦ coagulant concentration (mmol / L) ≦ C + 10 When the coagulant is acid C ≦ coagulant concentration (mmol / L) ≦ C + 30 C: Coagulation value (mmol / l) (g) The polymer latex and the coagulant are in contact with each other with stirring, and the peripheral speed at the tip of the stirring blade is 100 ≦ the peripheral speed at the tip of the stirring blade ≦ 800 (cm / s) ( H) Heat treatment condition Tv ≦ treatment temperature (° C.) ≦ Tv + 80 is provided.

The present invention will be described in detail below. Examples of the polymer latex to which the method of the present invention is applied include polymer latexes usually produced by emulsion polymerization. For example, styrene-butadiene rubber (SBR),
Rubber-like polymers such as acrylonitrile-butadiene rubber (NBR) and acrylic rubber. ABS such as acrylic resin, polystyrene, styrene-acrylonitrile copolymer
Examples thereof include resinous polymers such as resins, MBS resins, AES resins, and graft copolymers such as AAS resins.

A typical polymer latex of the present invention comprises a vinyl-based polymer latex and / or a rubber-modified vinyl-based polymer latex and is usually obtained by emulsion polymerization. These vinyl polymer latexes are obtained by polymerizing the following vinyl monomers or monomers copolymerizable therewith. The rubber-modified vinyl polymer latex is obtained by polymerizing the vinyl monomer shown below or a monomer copolymerizable therewith in the presence of the rubber polymer shown below.

The vinyl monomer is not particularly limited, but examples thereof include (meth) acrylic acid such as acrylic acid and methacrylic acid; alkyl acrylate monomer such as methyl acrylate, ethyl acrylate and butyl acrylate; Methacrylic acid alkyl ester type monomers such as methyl methacrylate and ethyl methacrylate; vinyl cyan type monomers such as acrylonitrile and methacrylonitrile; aromatic vinyl type monomers such as styrene and α-methylstyrene; vinyl chloride, odor Various monomers such as vinyl halide-based monomers such as vinyl chloride may be mentioned, and these may be used in combination of two or more kinds. Examples of preferable vinyl monomers include (meth) acrylic acid alkyl esters, vinyl cyan monomers, and aromatic vinyl monomers. As other copolymerizable monomers,
Examples thereof include maleimide-based monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide and N-cyclohexylmaleimide. When a maleimide-based monomer is used, heat resistance is improved and a polymer having excellent heat resistance can be obtained.

As the rubber-like polymer, polybutadiene,
Styrene-butadiene copolymer (styrene content 5-6
0% by weight is preferred. ), Styrene-isoprene-based copolymer, acrylonitrile-butadiene-based copolymer, ethylene-α-olefin-based copolymer, ethylene-α-olefin-polyene-based copolymer, acrylic rubber, butadiene-acrylic-based copolymer Examples thereof include polymer, polyisoprene, styrene-butadiene block copolymer, hydrogenated butadiene-based polymer, ethylene-based ionomer, and silicon-based rubber. These rubber-like polymers are used alone or in combination of two or more. Preferred rubbery polymers include polybutadiene, styrene-butadiene copolymers, acrylic rubbers, and silicone rubbers (in particular, unsaturated group-containing silicone rubbers are preferable). As the rubber-like polymer used for producing the rubber-modified vinyl polymer, a latex-like one is used. Examples of the polymer of the polymer latex include acrylic resins, polystyrene, styrene-acrylonitrile copolymers, (α-methyl) styrene- (acrylonitrile) -maleimide monomer copolymers, and ABS resins, MBS resins, Examples thereof include resinous polymers such as rubber-modified vinyl polymers such as AES resin and AAS resin.

As the coagulant of the present invention, those generally used for coagulating latex can be used. Examples thereof include inorganic acids such as hydrochloric acid and sulfuric acid, organic acids such as acetic acid and formic acid, and metal salts of these acids. In addition, a polymer flocculant and the like can also be used in combination. Examples of the above metal salts include calcium chloride, calcium nitrate, aluminum chloride, aluminum sulfate, magnesium sulfate and the like. In the present invention, polyvalent metal salts and inorganic acids are preferred. More preferably, calcium chloride,
Examples thereof include magnesium sulfate and sulfuric acid. Examples of the polymer flocculant include polyacrylamide. Further, the salt and the acid can be used in combination.

The method of recovering the polymer of the present invention comprises a first step of adding and mixing a coagulant having a coagulation value of not more than a coagulation value to the polymer latex when coagulating the polymer latex, and the coagulation value of the polymer latex being not less than the coagulation value. It is a method of recovering a polymer, which comprises a second step of coagulating at a coagulant concentration of The technical feature of the present invention, which is a feature of the present invention, is that the first step is performed before the second step, which is superior to the conventional polymer recovery method in the second step only in powder characteristics. ing. The amount of the coagulant added in advance in the first step is such that the coagulant concentration is equal to or lower than the coagulation value. The coagulant concentration is in the following range. 0.3 × (coagulation value) ≦ coagulant concentration in latex (mmol / L) ≦ 0.9 × (coagulation value), preferably 0.4 × (coagulation value) ≦ coagulant concentration in latex (mmol / L)
L) ≦ 0.8 × (coagulation value). If the concentration of the coagulant in the latex is less than 0.3 times the coagulation value, coagulation will not be sufficiently completed inside the coagulated particles in the subsequent step, and the water content of the coagulated particles will increase and the bulk density will also decrease. Coagulation value 0.9
When the amount is more than double, there is a problem that a part of solidification starts and stable solidification operation cannot be performed. The temperature at which the coagulant is added to and mixed with the polymer latex in advance is an arbitrary temperature at which coagulation does not occur, for example, a temperature between 10 ° C and 60 ° C. In the second step, the coagulant is added so that the coagulant concentration is equal to or higher than the coagulation value under the coagulation conditions of the polymer latex in the first step, and the other conditions are generally used to recover the polymer. The amount of the coagulant actually added in the second step is the remaining amount obtained by subtracting the amount of the coagulant previously added in the first step from the amount of the coagulant having the set coagulant concentration. The preferable condition of the second step is that the content of the rubber-like polymer in the polymer latex is less than 60% by weight and 60% by weight.
It is different depending on the above cases, and it is preferable that the condition is the condition of claim 2 in the former case and the condition of claim 3 in the latter case.

Claims 2 and 3 will be described below.
The content of the rubbery polymer is 0 to 60 at the solidification temperature condition.
When the polymer latex is less than wt%, Tv-2
0 <solidification temperature <Tv + 30, preferably Tv-10
<Coagulation temperature <Tv + 10. Freezing temperature is Tv-
If it is lower than 20, fine powder is produced. Freezing temperature is Tv + 30
If it is higher, the solidified particles are more likely to be fused, coarse particles and lumps are generated, and the slurry concentration cannot be increased. When the content of the rubbery polymer is 60% by weight or more, the polymer latex has Tv-40 <coagulation temperature <Tv + 20, preferably Tv-30 <coagulation temperature <Tv + 10.
If the solidification temperature is lower than Tv-40, fine powder is produced. If the coagulation temperature is higher than Tv + 20, the coagulated particles are likely to be fused,
Coarse particles and lumps are not formed, and the slurry concentration cannot be increased.

When the coagulant concentration is C (coagulation value) or less, coagulation does not sufficiently occur and the coagulation agent is in an uncoagulated state. Also, (b)
When the value on the right side is exceeded in the coagulation concentration range formula of each coagulant shown in (f), fine particles are generated and there is a problem in handling.
The stirring conditions are such that when the content of the rubber-like polymer is a polymer latex of 0 to less than 60% by weight, 10 ≦ peripheral speed of the stirring blade tip ≦ 500 (cm / s), preferably 60 ≦ peripheral speed ≦ 3.
It is 60 (cm / s). If the peripheral speed is less than 10 cm / s, a large lump will be generated. The peripheral speed is 500 cm / s
If it exceeds the range, fine powder is generated and there is a problem in handling.
When the content of the rubber-like polymer is not less than 60% by weight, the polymer latex has a peripheral speed of 100 ≦ the stirring blade tip peripheral speed ≦ 8.
00 (cm / s), preferably 150 ≦ peripheral speed ≦ 750
(Cm / s). If the peripheral speed is less than 100 cm / s, a large lump will be generated. Further, when the peripheral speed exceeds 800 cm / s, fine powder is generated and there is a problem in handling.

When the heating condition is lower than Tv, the effect of the heat treatment is small, and the effect of increasing the bulk density and reducing the water content in the recovered coagulated particles does not appear. The content of rubbery polymer is 0-60
When the content of the polymer latex is less than wt%, Tv ≦ treatment temperature (° C.) ≦ Tv + 50 ° C., and when it exceeds Tv + 50 ° C., solidified particles are fused to each other to form a lump, which makes stable operation impossible. Furthermore, the slurry concentration cannot be raised to a practical range. When the content of the rubber-like polymer is 60% by weight or more, the polymer latex has Tv ≦ treatment temperature (° C.)
≦ Tv + 80 ° C., and when Tv + 80 ° C. is exceeded, the solidified particles are fused with each other to form a lump, and stable operation cannot be performed. Furthermore, the rally concentration cannot be raised to a practical range. Also,
The heat treatment time is usually 10 minutes ≦ treatment time ≦ 180
Minutes. Preferably, 20 minutes ≦ treatment time ≦ 120 minutes. If it is shorter than 10 minutes, the effect of heat treatment does not appear. 18
If it exceeds 0 minutes, the physical properties such as the hue of the resin will be impaired, and the apparatus will become too large, which is not economical. In the present invention, since the amount of the coagulant is smaller than that in the conventional method, the uncoagulated latex sometimes remains slightly, and the generation of fine powder, the clogging of the filter cloth of the dehydrator in the subsequent step, etc. There are cases where it is not preferable in respect of. Therefore, it is preferable to add the coagulant after the coagulation.

The amount of the coagulant to be added is such that when the coagulant is a salt and the coagulant has a monovalent cation, the concentration in the system is 200 mmol / l or more. Is 5 mmol / l or more. When the cation is trivalent, it is preferable to add it so that the concentration in the system increases by 2 mmol / l or more. When the coagulant is an acid, it is preferable to add it so that the concentration in the system increases by 5 mmol / l or more. The coagulation method of the present invention is a continuous method in which a polymer latex or a coagulant is continuously and / or sequentially supplied and a coagulated slurry is continuously and / or sequentially discharged, or a polymer latex or a coagulant is supplied. After that, the mixture can be left to stir for a certain period of time, and then the solidified slurry can be discharged in a batch system.

The process of the method for coagulating the polymer latex of the present invention is not particularly limited, and a commonly used method can be used. For example, the polymer latex, the coagulant (aqueous solution), and optionally water are continuously or batchwise (a), (b),
(C), (D) or (E), (F), (G),
The solidified slurry is obtained by supplying under the condition of (h). The shape of the stirring blade used for mixing and stirring when obtaining this solidified slurry is not particularly limited,
Commonly used blades such as paddle blades, turbine blades, propeller blades, gate blades, ribbon blades can be used. Next, the coagulated polymer particles in the coagulated slurry obtained above can be separated, washed with water if necessary, and dried to obtain dried polymer particles. The polymer particles can be separated by a horizontal belt filter, a centrifugal dehydrator, a vertical pressure filter or the like. Further, the dehydrated coagulated particles can be dried by a twin-screw extruder equipped with a dehydration slit.

[0016]

EXAMPLES The method of the present invention will be specifically described below with reference to examples, but these do not limit the scope of the present invention. Physical property measuring method Coagulation value The polymer latex is diluted with water so that the solid content concentration becomes 0.20%. This diluted polymer latex 10c
c in a test tube, 10 cc of coagulant aqueous solution with various concentrations
Was added, mixed well, and allowed to stand in a constant temperature bath at 30 ° C.
Then, the presence or absence of precipitate formation after 1 hour was examined, and the lowest concentration of the coagulant at which precipitation occurred (mmol / l after mixing) was taken as the coagulation value. Vicat softening point The Vicat softening point is JIS K7206, in which the polymer is previously collected from the polymer latex that is coagulated for coagulation and dried.
Measure according to the method of. The load used for measurement is 1K
gf. Bulk density Measured according to JIS-K-6721. (Unit: g
/ Ml) Particle size Up to a particle size of 1000 μm, the particle size distribution is determined by a laser diffraction / scattering type particle size distribution measuring device (manufactured by Horiba Ltd.). For those exceeding 1000 μm, it is determined by image processing. Average particle size d _{50 The} particle size is the cumulative value of 50% obtained from the cumulative distribution curve of the particle size distribution. Amount of fine particles Determined by the amount of resin passing through a 200 mesh mesh.

Example 1 As a polymer latex, a graft copolymer comprising 10% by weight of butadiene obtained by graft copolymerizing styrene, methyl methacrylate and acrylonitrile on polybutadiene, 23% by weight of styrene, 10% by weight of acrylonitrile and 57% by weight of methyl methacrylate. The combined latex was used as a raw material. The solid content concentration of this graft copolymer latex was 30% by weight, the coagulation value measured using an aqueous solution of calcium chloride (coagulant) was 11 mmol / l, and the Vicat softening point was 96 ° C. The coagulant used for the coagulation operation is a 2% calcium chloride aqueous solution. Calcium chloride was added to the above graft copolymer latex in advance so as to be 5 mmol / l. The above latex in which a calcium chloride 5 mmol / l equivalent amount was added to a place stirred at a tip speed of 160 cm / s in a closed coagulation tank with a stirrer (2-stage inclined paddle blade, blade diameter 7.5 cm) having an internal volume of 6 liters. 200ml / min, 2m calcium chloride aqueous solution 40m
1 / min, water, 360 ml / min were added continuously. The coagulant concentration in the coagulation tank was 14 mmol / l. The temperature of the coagulation tank was controlled to 88 ° C by jacket heating to continuously coagulate, and after adding a coagulant equivalent to 7 mmol / l to the coagulation slurry continuously discharged from the coagulation tank, to 110 ° C. And heat treated for 40 minutes. afterwards,
Using a centrifuge, the polymer components were separated, washed with water and dehydrated to obtain wet powder. This wet powder is dried with hot air (70 ℃ × 7H
r) to obtain dry polymer particles. The results are shown in Table 1.

Example 2 100 ml / min of 2% calcium chloride aqueous solution and 30% of water so that the concentration of the coagulant in the coagulation tank was 32 mmol / l.
The same procedure as in Example 1 was carried out except that the procedure was changed to 0 ml / min. Example 3 Example 3 was repeated except that the solidification temperature was 97 ° C. Example 4 Example 4 was repeated except that the stirrer was rotated at a peripheral speed of 220 m / s. Example 5 The procedure of Example 1 was repeated, except that the heat treatment after completion of solidification was performed at 110 ° C. for 120 minutes.

Example 6 20% by weight of acrylonitrile as a polymer latex,
A raw material was obtained by copolymerizing 1% by weight of styrene, 78% by weight of α-methylstyrene and 1% by weight of methyl methacrylate. The solid content concentration of this polymer latex was 30% by weight. The coagulation value measured using calcium chloride was 3 mmol / l. The Vicat softening point was 122 ° C. Calcium chloride was added to the polymer latex in advance so as to be 1 mmol / l in the latex and stirred. Using this polymer latex,
Solidification was performed in the same manner as in Example 1 so that the solidification temperature was 113 ° C., the coagulant concentration was 5 mmol / l, and the peripheral speed of the stirring blade was 180 m / min. The heat treatment was carried out at 140 ° C. for 90 minutes after additionally adding a coagulant equivalent to 5 mmol / l. The results are shown in Table 1.

Example 7 Butadiene 62 obtained by graft copolymerizing styrene and acrylonitrile onto polybutadiene as a polymer latex.
The raw material was a graft copolymer latex composed of 10% by weight of styrene and 10% by weight of acrylonitrile. The solid content of this graft copolymer latex is 3
The coagulation value measured with an aqueous solution of calcium chloride (coagulant) at 0% by weight was 12 mmol / l, and the Vicat softening point was 61 ° C. The coagulant used for the coagulation operation is a 2% calcium chloride aqueous solution. Calcium chloride is added to the latex in advance so that the coagulant concentration becomes 7 mmol / l. 200 ml / min of the above latex was continuously added to a place where the mixture was stirred at a tip speed of 300 cm / s in a closed coagulation tank with a stirrer (two-stage inclined paddle blade, blade diameter 7.5 cm) having an internal volume of 6 liters, and 2% calcium chloride. 40 aqueous solution
ml / min, water, 360 ml / min were added. The coagulant concentration in the coagulation tank was 14 mmol / l. The temperature of the coagulation tank is controlled to 45 ° C by jacket heating to continuously coagulate, and after adding an additional amount of 7 mmol / l of coagulant to the coagulation slurry continuously discharged from the coagulation tank, 110 ° C. And heat-treated for 40 minutes. Then, using a centrifuge, the polymer component was separated, washed with water, and dehydrated to obtain a wet powder. This wet powder is dried with hot air (70 ℃ × 7H
r), dry polymer particles were obtained. The results are shown in Table 1.

[0021]

[Table 1]

Examples 1 to 7 are examples carried out within the scope of the present invention, in which the amount of fine powder is small and the powder characteristics are good, and the object of the present invention is achieved. On the other hand, Comparative Example 1 was carried out in the same manner as in Example 1 except that calcium chloride was added to the polymer latex in advance so as to be 1 mmol / l. In Comparative Example 1, the amount of the coagulant added to the polymer latex in advance is less than the range of the present invention, and the effect of the present invention does not appear. Comparative Example 2 was carried out in the same manner as in Example 1 except that calcium chloride was added to the polymer latex in advance so as to be 11 mmol / l. In Comparative Example 2, since the amount of the coagulant added to the polymer latex in advance exceeds the range of the present invention, some coagulation occurs, stable coagulation operation cannot be performed, and a large amount of fine powder is also contained. In Comparative Example 3, calcium chloride was added to the polymer latex in an amount of 5 mmol / l. The concentration of coagulant in the coagulation tank is 9 mmol
25 ml of 2% calcium chloride aqueous solution so that
/ Min and water was changed to 375 ml / min, and the same procedure as in Example was carried out. In Comparative Example 3, the coagulant concentration is less than the range of the present invention, and coagulation hardly occurs.

Example 8 has a solidification temperature of 1 in Example 1.
In this example, the temperature is 30 ° C. and the peripheral speed of the stirring blade is 450 cm / s. Example 9 is an example in which the solidification temperature is 70 ° C. and the peripheral speed of the stirring blade is 160 cm / s in Example 1. Example 10 is an example carried out in the same manner as in Example 1 except that the calcium chloride aqueous solution was changed to 180 ml / min and the water was changed to 220 ml / min. In Example 11, the peripheral speed of the stirring blade in Example 1 was 8 cm / s.
Is an example of. Example 12 is an example in which the peripheral speed of the stirring blade was set to 600 cm / s in Example 1. Example 13 is an example in which the heat treatment temperature is 90 ° C. in Example 1. Example 14 is an example in which the heat treatment time was 8 minutes in Example 1. Example 15 is an example in which the heat treatment temperature was set to 150 ° C. in Example 1. Example 16 is an example carried out in the same manner as in Example 6 except that the heat treatment condition in Example 6 was changed to 115 ° C. × 90 minutes.

[0024]

As the most general method for coagulating polymer latex, a method in which the polymer latex and a coagulant are continuously supplied to a coagulation tank for coagulation and aggregation is known. There is. However, these methods have problems that there are many fine powders and the powder characteristics are inferior. The present invention limits the generation of fine powder particles by controlling the particle size by limiting the pretreatment method of the polymer latex in the coagulation step, the coagulant concentration, the coagulation temperature and the stirring conditions to a specific range, and the powder characteristics. It is a modification of.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Teizo Fukuda 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd.

Claims (3)

[Claims] 1. When coagulating a polymer latex, the coagulant concentration in the polymer latex is 0.3 × in advance.
(Coagulation value) ≤ Coagulant concentration in latex (mmol / L) ≤
A coagulant is added to and mixed with the polymer latex so as to be 0.9 × (coagulation value), and further a coagulant is added to coagulate at a coagulant concentration equal to or higher than the coagulation value of this polymer latex. A method for recovering a polymer, comprising: 2. A vinyl-based polymer and / or a rubber-modified vinyl-based polymer, wherein the content of the rubber-like polymer is 0.
When coagulating a polymer latex whose amount is less than 60% by weight, a coagulant having a coagulation value or less is previously added to and mixed with the polymer latex, and the polymer latex is mixed with the following (a), (b) and ( After solidifying under the condition of c),
A method for recovering a polymer, which comprises heat treatment under the condition (d). (A) Coagulation temperature (° C) Tv-20 <Coagulation temperature <Tv + 30 where Tv; Vicat softening point of polymer to be recovered (b) Coagulant concentration The coagulant is a salt and the cation of the coagulant is When monovalent C ≦ coagulant concentration (mmol / L) ≦ C + 2000, when coagulant is a salt and cation of the coagulant is divalent C ≦ coagulant concentration (mmol / L) ≦ C + 30, coagulation When the agent is a salt and the cation of the coagulant is trivalent, C ≦ coagulant concentration (mmol / L) ≦ C + 10 When the coagulant is acid C ≦ coagulant concentration (mmol / L) ≦ C + 30 C: Coagulation value (mmol / l) (C) The polymer latex and the coagulant are contacted with stirring, and the peripheral speed of the tip of the stirring blade is 10 ≦ the peripheral speed of the stirring blade ≦ 500 (cm / s) ( D) Heat treatment condition Tv ≤ treatment temperature (° C) ≤ Tv + 50 3. When coagulating a polymer latex comprising a rubber-modified vinyl polymer and having a rubbery polymer content of 60% by weight or more, a coagulant having a coagulation value or less is previously added to the polymer latex. A method for recovering a polymer in which the polymer latex is mixed and coagulated under the following conditions (e), (f) and (g) and then heat-treated under the condition (h). (E) Coagulation temperature (° C) Tv-40 <Coagulation temperature <Tv + 20 where Tv; Vicat softening point of polymer to be recovered (F) Coagulant concentration The coagulant is a salt and the cation of the coagulant is When monovalent C ≦ coagulant concentration (mmol / L) ≦ C + 2000, when coagulant is a salt and cation of the coagulant is divalent C ≦ coagulant concentration (mmol / L) ≦ C + 30, coagulation When the agent is a salt and the cation of the coagulant is trivalent, C ≦ coagulant concentration (mmol / L) ≦ C + 10 When the coagulant is acid C ≦ coagulant concentration (mmol / L) ≦ C + 30 C: Coagulation value (mmol / l) (g) The polymer latex and the coagulant are in contact with each other with stirring, and the peripheral speed at the tip of the stirring blade is 100 ≦ the peripheral speed at the tip of the stirring blade ≦ 800 (cm / s) ( H) Heat treatment condition Tv ≦ treatment temperature (° C.) ≦ Tv + 80