JPH07138376A - Bead-shaped particles and method for producing the same - Google Patents

Abstract

(57) [Summary] [Object] To provide 0.5 to 5 mm bead-shaped particles obtained by coagulating a polymer latex comprising a vinyl polymer and / or a rubber-modified vinyl polymer, and a method for producing the same. The purpose is to [Structure] A bead-shaped particle characterized in that the particle obtained by coagulating a polymer latex contains 90% by weight or more of a bead-shaped particle of 0.5 to 5 mm. The method for producing the beaded particles, wherein the polymer latex is coagulated at a specific coagulation temperature, a specific coagulant concentration and a specific stirring speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to polymer particles recovered from a polymer latex obtained by emulsion polymerization or the like and a method for producing the same, and more specifically to bead-shaped particles having a uniform particle size of 0.5 to 5 mm. The present invention relates to bead-shaped particles containing 90% or more of particles and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a polymer latex obtained by emulsion polymerization has a coagulant added thereto to obtain a powdery polymer. However, since the powder obtained by this method contains fine powder, the productivity is lowered in the subsequent dehydration, drying and pelletization, and there is an environmental problem due to powdering. Further, since it is powdery, it is difficult to handle as a molding material for a molded product, and it is necessary to once form a dry powder, pelletize it with a pellet extruder, and perform molding.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in the background of the above-mentioned prior art, and is in the form of beads (having a particle size of 0. 5 to 5 mm) of polymer particles and a method for producing the same.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, by limiting the solidification temperature, the coagulant concentration and the stirring blade tip speed in the solidification step to a specific range, The inventors have completed the present invention by achieving the solution of the problem and finding that beads-like particles can be obtained.

The present invention relates to particles obtained by coagulating a polymer latex (A) comprising a vinyl polymer and / or a rubber-modified vinyl polymer, the beads having a particle diameter of 0.5 to 5 mm. Diameter of 90% by weight or more of bead-shaped particles, and particle size obtained by coagulating polymer latex (A) in an aqueous system under the following conditions (a), (b) and (c): 0.5-5 mm
There is provided a method for producing beaded particles containing 90% by weight or more of the beaded particles. (A) Coagulation temperature (Tm-20 ° C) ≤ coagulation temperature ≤ (Tm + 30 ° C) where Tm is the softening point (° C) of the recovered polymer (b) Coagulant concentration (a) When the coagulant is a salt, It is determined as follows depending on the valence of the cation. In case of monovalent C ≦ coagulant concentration ≦ C + 2000 mmol /
l In the case of divalent C ≦ coagulant concentration ≦ C + 30 mmol / l In the case of trivalent C ≦ coagulant concentration ≦ C + 10 mmol / l (b) When the coagulant is an acid C ≦ coagulant concentration ≦ C + 30 mmol / l where C is the coagulant Deposition value (mmol / l) (C) Stirring speed 10 ≦ stirring blade tip speed ≦ 300 cm / S

The present invention will be described in detail below. First, the method for obtaining the softening point (Tm) and the coagulation value shown in (a) and (b) of the present invention will be described. The softening point (m) is determined by JIS after the polymer is recovered from the polymer latex used for coagulation and dried.
The Vicat softening point is measured according to the method of K7206, and this value is defined as the softening point (Tm) of the present invention. The coagulation value (C) was determined by the method shown below using the polymer latex used for coagulation and the coagulant used for coagulation. The polymer latex is diluted with water to a concentration of 0.20%. 10 cc of this polymer latex was placed in a test tube, 10 cc of coagulant aqueous solution of various concentrations was added, mixed well, and allowed to stand in a constant temperature bath at 30 ° C. The presence or absence of precipitate formation after 1 hour was examined, and the lowest concentration at which precipitation occurred (mmol / l after mixing) was taken as the coagulation value.

The polymer latex (A) of the present invention comprises a vinyl polymer latex and / or a rubber-modified vinyl polymer latex. These are usually obtained by emulsion polymerization. The vinyl polymer latex can be 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-based monomer is not particularly limited, but examples thereof include (meth) acrylic acid such as acrylic acid and methacrylic acid; alkyl acrylate-based monomer such as methyl acrylate, ethyl acrylate and butyl acrylate. Methacrylic acid alkyl ester type monomers such as methyl methacrylate and ethyl methcrylate; vinyl cyan type monomers such as acrylonitrile and methacrylonitrile; aromatic vinyl type monomers such as styrene and α-methylstyrene; Various monomers such as vinyl halide monomers such as vinyl and vinyl bromide may be mentioned, and these may be used in combination of two or more kinds. Preferred vinyl monomers are (meth) acrylic acid alkyl ester, vinyl cyan monomer, and aromatic vinyl monomer, and more preferably (meth) acrylic acid alkyl ester, vinyl cyan monomer. At least two kinds selected from a monomer and an aromatic vinyl-based monomer.

Examples of other copolymerizable monomers 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).

The rubber-like polymer used in the production of the rubber-modified vinyl polymer is a latex-like one. Examples of the polymer of the polymer latex (A) include resins such as acrylic resins, polystyrene, styrene-acrylonitrile copolymers, and rubber-modified vinyl polymers such as ABS resins, MBS resins, AES resins, and AAS resins. Polymers may be mentioned. The preferred polymer latex of the present invention is the rubber-modified vinyl polymer latex shown above. By using this latex, the efficiency which is the object of the present invention is further enhanced. The content of the rubber-like polymer in the polymer latex (A) is preferably 60% by weight or less, more preferably 55% by weight or less, and particularly preferably 50% by weight or less. In addition, if the content of the rubber-like polymer is 45% by weight or less, and especially 40% by weight or less, the objects and effects of the present invention are further enhanced.

As the coagulant of the present invention, those generally used for coagulating latex can be used. For example, inorganic acids such as hydrochloric acid and sulfuric acid, organic acids such as acetic acid and formic acid, or 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 preferred are sulfuric acid, calcium chloride and magnesium sulfate, particularly preferred are calcium chloride and magnesium sulfate, and most preferred is calcium chloride. Examples of the polymer flocculant include polyacrylamide. Further, the salt and the acid can be used in combination.

A preferable method for producing the beaded particles of the present invention is to polymerize the polymer within the following conditions (a), (b) and (c) by appropriately selecting the conditions for forming the beaded particles of the present invention. Coagulate the latex. The temperature of (a) is
“(Tm−20 ° C.) ≦ solidification temperature ≦ (Tm + 30 ° C.)”, preferably “(Tm−10) ≦ solidification temperature ≦ (Tm
+ 10 ° C.) ”(softening point −20 ° C.), fine powders are formed at low temperatures, while (softening point +30).
At a temperature higher than the temperature (° C.), The solidified particles are likely to be fused, coarse particles are generated, and the solidified slurry concentration cannot be increased.

The concentration of the coagulant in (b) is (a) when the coagulant is a salt, and when the coagulant is monovalent depending on the valence of the cation, C ≦ coagulant concentration ≦ C + 2000 mmol / l; 2
In case of valency, C ≦ coagulant concentration ≦ C + 30 mmol / l; 3
In case of valence, C ≦ coagulant concentration ≦ C + 10 mmol / l, preferably in case of valence C ≦ coagulant concentration ≦ C + 1
500 mmol / l; if divalent, C ≦ coagulant concentration ≦ C
+20 mmol / l; if trivalent, C ≦ coagulant concentration ≦ C
+8 mmol / l. (B) When the coagulant is an acid C ≦ coagulant concentration ≦ C + 30 mmol / l, and more preferably C ≦ coagulant concentration ≦ C + 20 mmol / l. Below the C value, coagulation does not occur sufficiently and uncoagulation exists. If the coagulant concentration exceeds the above concentration, fine powder is produced.

Further, a preferred coagulant concentration when two or more coagulants containing a monovalent, divalent, or trivalent cation and an acid are mixed and used is determined by the following method. The coagulation value of the coagulant containing a monovalent cation is C ₁ (mmol /
l), the concentration used is A (mmol / l); the coagulation value of the coagulant containing divalent cations is C ₂ (mmol / l), the concentration used is B (mmol / l); trivalent cation The coagulation value of the coagulant containing ions is C ₃ (mmol / l), the concentration used is C (mmol / l); the coagulant is acid, and the coagulation value is C
₄ (mmol / l), the concentration used is D (mmol / l
In the case of l), the coagulant concentration is represented by a converted coagulant concentration C _CONV converted into a divalent coagulant. That is, C _CONV = A (C ₂ / C ₁ ) + B + C (C ₂ / C ₃ ) + D
(C ₂ / C ₄₎ using the terms of coagulant concentration, determine the析値(C _M) coagulation of the mixed coagulant to a predetermined ratio. And in this case,
It solidifies under the following conditions. C _M ≤ reduced coagulant concentration ≤ C _M +30

(C) The stirring speed is 1 at the tip of the stirring blade.
0 ≦ speed of stirring blade tip ≦ 300 (cm / S), preferably 30 ≦ speed of stirring blade tip ≦ 250 (cm / S)
Is. When the stirring blade tip speed is less than 10 cm / S, the mixing is insufficient and particles having a uniform particle size are not generated. Further, when the stirring blade tip speed exceeds 300 cm / S, stirring results in particles of less than 0.5 mm. Also,
The solidified particle size can be controlled by increasing or decreasing the speed of the stirring blade tip.

Heat treatment can also be performed to improve the mechanical properties of the solidified particles and the powder properties such as the bulk density. The heat treatment conditions are preferably Tm ≦ treatment temperature ≦ Tm + 50, more preferably Tm + 10 ≦ treatment temperature ≦ Tm + 40. When it is lower than Tm, the effect of heat treatment is small, and the effects of increasing the bulk density and reducing the water content in the recovered coagulated particles do not appear. If it exceeds Tm + 50 ° C., the solidified particles are fused with each other to form an agglomerate, which makes stable operation impossible. Also, the slurry concentration cannot be increased. The heat treatment time is preferably 5 minutes ≦ treatment time ≦ 180
Minutes, more preferably 10 minutes ≦ treatment time ≦ 120 minutes. If it is shorter than 5 minutes, the effect of the heat treatment is small, and the effects of increasing the bulk density and reducing the water content in the recovered coagulated particles do not appear. If it exceeds 180 minutes, the physical properties such as the hue of the resin will be impaired, and the equipment will be large, which is not economical. The heat treatment time here is an average residence time in continuous operation.

The beaded particles obtained by coagulating the polymer latex (A) in an aqueous system and containing 90% by weight or more of the beaded particles having an average particle size of 0.5 to 5 mm are novel. The average particle diameter is 0.5 to 5 mm, preferably 0.7 to 4 mm. If the particle size is less than 0.5 mm, there is a problem with powder. On the other hand, when it exceeds 5 mm, the cleaning efficiency is lowered and the content of impurities is increased. Then, the handleability and workability are deteriorated. 0.5-5m above
The content of the beaded particles of m is 90% by weight or more. If the content is less than 90% by weight, the object of the present invention cannot be achieved. The particle size was measured using a laser diffraction / scattering type particle size distribution measuring device. However, particles having a particle size of more than 1 mm were obtained by image analysis. The narrower the particle size distribution of the beaded particles of the present invention, the more uniform the particles are, and therefore the narrower the particle size distribution is. The spread obtained by the following formula is a measure showing the particle size distribution, and therefore the preferred spread is 3
It is the following. Spread = (d ₉₀ −d ₁₀ ) / d ₅₀

An example of the method for producing the beaded particles of the present invention will be shown. The polymer latex, the coagulant (aqueous solution), and optionally water are continuously or batchwise supplied so as to satisfy the condition (b) of the present invention to obtain a coagulated slurry. During and / or after the supply of the respective components, the solidified slurry is heated at the solidification temperature of (a) of the present invention. During heating, stirring is performed at the stirring speed of (c) of the present invention. The polymer particles are aggregated by this heating and stirring, and the bead-shaped particles of the present invention are produced. However, the above-mentioned (a), (b), (c) and the solidification temperature are appropriately selected under the condition that the beaded particles having the shape of the present invention can be obtained. The shape of the stirring blade used for this stirring is not particularly limited, and may include paddle blades, turbine blades, propeller blades,
Commonly used blades such as gate type blades can be used.

In the present invention, the above bead-shaped particles are separated, washed with water and dried if necessary. Examples of the separation method include the following methods. That is, it can be dehydrated and washed and separated by a centrifugal dehydrator or the like. Further, it is dried by a fluidized drier and collected as dried particles.
As a result, conventionally, the solidified particles were pelletized using an extruder and colored and molded using the pellets, whereas the beaded particles of the present invention can be directly fed to the molding machine and pelletized. It is possible to omit the step of. Even when pelletizing the beaded particles of the present invention, compared to conventional powders, handleability in the pelletizing step,
Higher pellet productivity.

[0021]

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. Example 1 As a polymer latex, a graft copolymer comprising 20% by weight of butadiene obtained by emulsion graft copolymerizing styrene, methyl methacrylate and acrylonitrile in the presence of polybutadiene rubber, 18% by weight of styrene, 5% by weight of acrylonitrile and 57% by weight of methyl methacrylate. Polymer latex was used as a raw material. The solid content of this graft copolymer latex was 30% by weight, the coagulation value measured using a 0.2% by weight calcium chloride (coagulant) aqueous solution was 11 mmol / l, and the Vicat softening point was 90 ° C. It was
A 2 wt% calcium chloride aqueous solution was used as a coagulant. In a coagulation tank with an internal volume of 10 liters equipped with a stirrer, 300 ml / min of the above latex was continuously added, 83.3 ml / min of a 2 wt% calcium chloride aqueous solution, and 6 ion-exchanged water was added.
16.7 ml / min was added. The coagulant concentration in the coagulation tank is 1
It was 5 mmol / l. The temperature of the coagulation tank was controlled to 95 ° C. by heating the jacket, and the stirring speed was such that the stirring blade tip speed was 100 cm / S. The spherical particles continuously discharged from the coagulation tank which had been continuously coagulated were separated by a centrifugal dehydrator, polymer components were separated, washed with water, dehydrated and dried to obtain dried spherical particles. The results are shown in Table 1.

Example 2 166.5 ml / mL of a 2 wt% calcium chloride aqueous solution was prepared so that the concentration of the coagulant in the coagulation tank was 30 mmol / l.
The same procedure as in Example 1 was carried out except that the ion exchanged water was 533.5 ml / min. The results are shown in Table 1.

Example 3 Example 3 was repeated except that the solidification temperature was 110 ° C. The results are shown in Table 1.

Example 4 Example 4 was repeated except that the stirring speed was 200 cm / S at the tip speed of the stirring blade. The results are shown in Table 1.

Comparative Example 1 Example 1 was repeated except that the solidification temperature was 60 ° C. The results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated except that the solidification temperature was 140 ° C. The results are shown in Table 1.

Comparative Example 3 The coagulant concentration in the coagulation tank was adjusted to 5 mmol / l,
The same procedure as in Example 1 was carried out except that the 2 wt% calcium chloride aqueous solution was 27.8 ml / min and the ion-exchanged water was 672.2 ml / min. The results are shown in Table 1.

Comparative Example 4 333 ml / min of a 2 wt% calcium chloride aqueous solution was added so that the concentration of the coagulant in the coagulation tank was 60 mmol / l.
The same procedure as in Example 1 was repeated except that ion-exchanged water was used at 367 ml / min. The results are shown in Table 1.

Comparative Example 5 The procedure of Example 1 was repeated except that the stirring speed was 5 cm / S at the stirring blade tip speed. The results are shown in Table 1.

Comparative Example 6 The procedure of Example 1 was repeated except that the stirring speed was 600 cm / S at the stirring blade tip speed. The results are shown in Table 1.

In Examples 1 to 4, spherical particles containing 90% or more of 0.5 to 5 mm spherical particles were produced, and the object of the present invention was achieved. On the other hand, in Comparative Example 1, the solidification temperature was below the range of the present invention, the amount of fine powder was large, and spherical particles could not be obtained. Comparative Example 2 was a case where the solidification temperature exceeded the range of the present invention, and the fusion of the polymer particles was so vigorous that the operation was impossible. In Comparative Example 3, the coagulant concentration was less than the range of the present invention, and almost no coagulation occurred. In Comparative Example 4, the coagulant concentration exceeded the range of the present invention, the amount of fine powder was large, and spherical particles were not formed. In Comparative Example 5, the stirring speed is less than the range of the present invention, and coarse particles are generated due to insufficient mixing. In Comparative Example 6, the stirring speed exceeded the range of the present invention, and the particles were uniform, but the target particle size could not be obtained.

[0032]

[Table 1]

[0033]

As a conventional method for recovering a polymer from a polymer latex, a coagulant is generally added to the polymer latex to agglomerate the polymer, which is then heated to enlarge the polymer particles. Although it was separated by a separator to obtain a powdery polymer, since it contains many fine powder particles, various problems occur. The present invention is 0.5 to 5 without fine powder particles.
The present invention provides a bead-shaped particle containing 90% by weight or more of a bead-shaped particle of mm, and by using this particle, it is possible to feed directly to a molding machine without pelletizing. In addition, the method for producing the beaded particles is lower than the coagulant concentration generally used conventionally, and the coagulant concentration in a specific range, the coagulation temperature in a specific range, and the stirring speed in a specific range,
Moreover, the generation of fine powder particles is suppressed by coagulating under the conditions that the conditions for obtaining the bead-shaped particles of the present invention are selected within the range of the conditions, and the bead-shaped particles containing 90% by weight or more of spherical particles of 0.5 to 5 mm are contained. To obtain particles. The beaded particles and the method for producing the same of the present invention are completely novel.

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

Claims (2)

[Claims] 1. Particles obtained by coagulating a polymer latex (A) comprising a vinyl polymer and / or a rubber-modified vinyl polymer in an aqueous system, the particle size of which is 0.
A bead-shaped particle comprising 90% by weight or more of a bead-shaped particle of 5 to 5 mm. 2. The method for producing beaded particles according to claim 1, wherein the polymer latex (A) is coagulated in an aqueous system under the following conditions. (A) Coagulation temperature (Tm-20 ° C) ≤ coagulation temperature ≤ (Tm + 30 ° C) where Tm is the softening point (° C) of the polymer to be recovered (b) Coagulant concentration (a) When the coagulant is a salt, It is determined as follows depending on the valence of the cation. In case of monovalent C ≦ coagulant concentration ≦ C + 2000 mmol /
l In the case of divalent C ≦ coagulant concentration ≦ C + 30 mmol / l In the case of trivalent C ≦ coagulant concentration ≦ C + 10 mmol / l (b) When the coagulant is an acid C ≦ coagulant concentration ≦ C + 30 mmol / l where C is the coagulant Deposition value (mmol / l) (C) Stirring speed 10 ≦ stirring blade tip speed ≦ 300 cm / S