JP2559833B2 - Continuous production method of powdery and granular polymer and method of controlling particle size of the polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a continuous method for producing a powdery or granular polymer, and more particularly to a continuous production of a powdery or granular polymer having a small amount of fine powder, a sharp particle size distribution and a controllable bulk specific gravity. The present invention relates to a production method and a method for controlling the particle diameter of a powdery polymer, and more particularly to a method for controlling the average particle diameter while maintaining the sharpness of the particle size distribution.

BACKGROUND ART A polymer latex obtained by an emulsion polymerization method or the like generally exists in a state in which polymer particles having a particle diameter of 1 μm or less are covered with an emulsifier and dispersed and suspended in water. Since the particle diameter is too small, solid-liquid separation is performed as it is. However, it is difficult to recover the polymer. As a conventional method for recovering a polymer from such a polymer latex, a method of directly separating it into powder or granules by using a spray dryer, a salt or an acid is mixed with the polymer latex to coagulate, and the temperature is raised. A method of heating and solidifying and then dehydrating and drying and collecting as a powder or granule has been widely used.

Further, in order to adjust the particle size of the obtained polymer particles, a method in which the polymer latex is dispersed and spheroidized in a specific solvent and then solidified (JP-A-52-68285), the polymer latex is coagulated A method in which the obtained slurry is mixed with an organic liquid which is hardly soluble in water and does not dissolve the polymer but which can be wetted (Japanese Patent Publication No. 59-5610), A method of mixing an insoluble but wettable organic liquid and a polymer latex in the presence of a coagulant (Japanese Patent Publication No. 59-5611), a droplet of the polymer latex in a coagulating atmosphere using a spray drying mechanism. Is proposed to disperse and semi-solidify, further solidify in a coagulating liquid, and then dehydrate and dry (JP-A-56-95905).

However, the method using the spray dryer of (1) requires a large amount of water to evaporate in order to dry the polymer latex accompanied by a large amount of water and requires a large amount of drying energy. There are problems that unevenness is likely to occur, the particle size distribution is wide, it is difficult to control the size and bulk specific gravity of the particles, and the apparatus cost is high.

The method of coagulating and solidifying is that when a conventional tank-type or tower-type coagulating and solidifying apparatus is used, the particle size distribution of the obtained polymer powder is wide, and therefore fine powder having a small particle size is used. It is mixed in a large amount and the handling of powder and granules is poor, especially about 40μ
There is a problem that fine powder of m or less is mixed with several weight% of the total weight of the particles and causes powdering. The average particle size was never set to 150 μm or less.

The method of (1) can control the particle size distribution and average particle size in the region where the particle size is 100 μm or more by spheroidizing.
It is difficult on the small particle size side of 0 μm or less, and it is necessary to treat a large amount of the solvent used after the spheroidizing treatment, and since the spherical latex particles are coagulated from the outside, the coagulation becomes non-uniform and the polymer There is a risk that problems such as fish eyes may occur during processing. This method is a method for producing a powdery granular polymer having a sharp particle size distribution, but the average particle size cannot be arbitrarily controlled while maintaining the sharpness of the particle size distribution. Although the other method is less than the method, it has a drawback that it is necessary to treat a large amount of the organic liquid in order to add 60 to 500 parts by weight of the organic liquid to 100 parts by weight of the polymer. It was This method is also a method for producing a powdery granular polymer having a sharp particle size distribution, but the average particle size cannot be arbitrarily controlled while maintaining the sharpness of the particle size distribution. Also in this method, in order to add 1 to 5 (volume ratio) of the organic liquid to the polymer volume 1,
It has the drawback of having to process large quantities of organic liquids.

Further, in the methods of and, since the addition of the organic liquid is a batch method, the viscosity increases sharply temporarily after the addition of the organic liquid even though the suspension protective agent and the surfactant are added. It has an unstable granulation process. The particle size distribution of the particles produced for this is the number of rotations of the stirrer,
The shape of the stirrer and the amount of the organic liquid used are greatly affected, and it is difficult to produce a large amount of particles having a controlled particle size distribution and bulk specific gravity at low cost. Further, the granulation behavior is different from the case of continuously supplying an organic liquid or the like, and it is no exaggeration to say that batch-type granulation is a technique different from continuous granulation.

Since the method is the same as the mechanism of spray drying, it is easy to obtain spherical powdery particles, but there is a drawback that the size of the particles is limited and the equipment becomes large due to coagulation using the gas phase. .

On the other hand, with the automation of powder metering and the increasing size of storage and transportation equipment, from the viewpoint of blocking phenomenon that powder particles solidify during storage and clogging of the transportation line due to insufficient fluidity of powder. However, the development of a granular polymer that is easy to handle is strongly desired. Recently, the functions required of resins have increased, and a single polymer alone cannot meet the demand for higher functionality, and it is often used as a mixture with other polymers and modifiers. In such a case, it is necessary to appropriately control the particle size so that the component fluctuation due to the segregation of the powder does not occur during storage and transportation.

Furthermore, when it is used as a mixture with other powdery or granular material, it must have an appropriate particle size so that the composition does not change due to segregation of the powder during storage and transportation. There is a strong demand for the development of a continuous manufacturing method for coalescing.

On the other hand, when the polymer is used as a mixture with other materials, the homogeneity of the mixture is further increased by melt-kneading with an extruder or the like. In such applications, it is necessary to minimize the number of powder particles having a particle size of 40 μm or less, which adversely affects the handling property of the powdery polymer, and to make the polymer powder as fine as possible in order to improve the dispersion during mixing. . As described above, there has been a strong demand for a method for controlling the particle size of powdery polymer particles which can control the average particle size while maintaining a sharp particle size distribution.

DISCLOSURE OF THE INVENTION The present invention has been made for the purpose of solving the problems in the conventional art. The continuous production method of the powdery granular polymer of the present invention is characterized in that the polymer latex obtained by the emulsion polymerization method is sequentially treated in the following step (I) and step (II).

Step (I): A step of coagulating the polymer latex to form a slurry in which coagulated particles are dispersed in water.

Step (II): The slurry obtained in Step (I), an organic liquid that is sparingly soluble in water and does not dissolve the polymer, and, if desired, a necessary amount of water in the following (a) to (c) are added. A step of continuously mixing and granulating under conditions.

(A); The proportion of water in the total mixture is 50 to 85% by weight.

(B); The amount of the organic liquid is 20 to less than 60 parts by weight based on 100 parts by weight of the polymer in the polymer latex.

(C); the temperature (° C) T of the entire mixture is averaged from 0.5 minutes to 0.5 ° C in the range of the following formula A-26 ≤ T ≤ A (A represents the azeotropic temperature (° C) of the mixture liquid). Hold for 1 hour.

Further, step (I) is carried out under the following conditions (d) and (e), and (d) the temperature at which the coagulation is lower than the glass transition temperature of the polymer in the polymer latex by 10 ° C. or more.

(E): The proportion of particles having a particle diameter of 100 μm or more in the coagulated particles is 1% by weight or less.

In addition, the proportion of the polymer in the total mixture in step (II) is preferably 10 to 30% by weight.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart of an exemplary apparatus used to practice the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION The latex used in the present invention is produced by a generally-used method, and contains an emulsifier, a polymerization initiator and other polymerization aids. The method of the invention is applicable to polymer latexes of coagulable homopolymers, copolymers and graft copolymers.

Examples of the homopolymer and copolymer latex include vinyl aromatic compounds such as styrene, dichlorostyrene and α-methylstyrene, vinyl cyan compounds such as acrylonitrile and methacrylonitrile, and alkyl acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate. , Alkyl methacrylate, further acrylic acid, vinyl chloride, vinylidene chloride, vinyl compounds such as vinyl acetate, butadiene, chloroprene, conjugated diolefins such as isoprene and its substitution products, homopolymers consisting of monomers such as ethylene glycol, Examples thereof include copolymers and latex mixtures of these polymers.

Examples of the graft copolymer latex include those obtained by grafting an elastic trunk polymer with a monomer or a monomer mixture capable of forming a hard polymer.

As the elastic trunk polymer constituting the graft copolymer latex, a diene-based polymer such as butadiene, isoprene, and chloroprene, an acrylate-based polymer having an alkyl group having 4 to 10 carbon atoms such as butyl acrylate and octyl acrylate, And copolymers with monomers copolymerizable therewith. Examples of the copolymerizable monomer include aromatic vinyl such as styrene and α-methylstyrene, methacrylic acid alkyl ester such as methyl methacrylate and ethyl methacrylate, and alkyl acryl having 1 to 3 carbon atoms such as methyl acrylate and ethyl acrylate. Examples thereof include vinyl cyanide compounds such as acid alkyl esters, acrylonitrile and methacrylonitrile.

As the monomer forming the hard polymer, styrene, α
-Aromatic vinyl such as methyl styrene, alkyl methacrylate such as methyl methacrylate, ethyl methacrylate and butyl methacrylate, vinyl cyanide compound such as acrylonitrile and methacrylonitrile, and vinyl halide such as vinyl chloride and vinyl bromide. . These monomers are used alone or in combination of two or more.

There are no restrictions on the coagulant used for coagulating the polymer latex in the present invention, and a commonly used coagulant can be used. For example, sodium chloride, calcium chloride, magnesium chloride, sodium sulfate, aluminum sulfate, zinc sulfate, magnesium sulfate, sodium carbonate, sodium hydrogen carbonate, ammonium chloride, metal salts such as potassium alum, sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, carbonic acid, Examples thereof include acids such as acetic acid and alcohols such as methanol and ethanol, and these can be used alone or in combination. The addition amount is not particularly limited, and is usually about 0.05 to the solid content of the polymer latex.
The amount is 50% by weight. Preferably about 0.1 to 20% by weight
Is. The time required for coagulation is very short, usually 0.1 minutes to 1 hour, preferably 0.5 minutes to 10 minutes as an average residence time.

When a coagulant is added to the polymer latex, the emulsified state of the polymer latex is destroyed and the polymer particles that have been emulsified and dispersed in the polymer latex aggregate to form aggregate particles (hereinafter referred to as “coagulated particles”). Abbreviated), and the coagulated particles are dispersed in water, which is the dispersion medium of the polymer latex, to form a slurry.

The temperature at which coagulation is carried out in carrying out the present invention is important for controlling the bulk specific gravity of the powdery granular polymer, and is more important than the glass transition temperature of the polymer contained in the polymer latex to be coagulated.
The temperature must be 10 ° C lower (hereinafter, abbreviated as "maximum coagulation temperature"). If the coagulation temperature is higher than the maximum coagulation temperature, the bulk specific gravity of the polymer powder will not increase unless a large amount of organic liquid is used in step (II). The cause of this is not clear, but it is presumed as follows. That is, when the coagulation temperature exceeds the maximum coagulation temperature, the particles constituting the coagulated particles (these are referred to as "basic particles" are generally referred to as "basic particles". It is considered that some of the polymer particles are fused to each other), and the surface of the polymer particles becomes tacky, and the polymer particles are easily fused firmly at the contact points with other basic particles.
As a result, coagulated particles having a stronger bonding force between the basic particles are generated than when coagulated at the maximum coagulation temperature or lower. On the other hand, coagulated particles are so-called sparse particles in which basic particles are sparsely aggregated. The coagulated particles with this sparse structure are
"Liquid cross-linking force" generated by the organic liquid added in I)
Due to the strong cohesive force due to and the rearrangement of the positions of the elementary particles caused by stirring or shaking, compaction is performed. As the solidification of the coagulated particles progresses, the organic liquid stored inside the coagulated particles appears on the surface of the consolidated coagulated particles. By the organic liquid on the surface, a "liquid cross-linking force" is formed between the coagulated particles, and the coagulated particles are further aggregated / consolidated to be particles having a desired size and apparent density. However,
As described above, the coagulated particles coagulated at a temperature higher than the maximum coagulation temperature have a strong bonding force between the basic particles, so that the process (II)
Therefore, the rearrangement of the positions of the basic particles is unlikely to occur, and the bulk specific gravity of the obtained powdery granular polymer becomes small. On the contrary, in order to obtain a powdery granular polymer having a large bulk specific gravity, i) a large cohesive force is generated between the basic particles in which the bond due to the fusion is not generated, and the bond due to the fusion is cut off to re-produce the basic particles. Alignment is likely to occur, and ii) even if the coagulated particles are not consolidated and the organic liquid occluded inside does not appear on the surface of the coagulated particles, the organic liquid is allowed to exist on the surface of the coagulated particles and It promotes the aggregation and consolidation between the "deposited particles".

It is considered that two points are necessary, and a large amount of organic liquid is required in the step (II).

Furthermore, when coagulating at a temperature exceeding the maximum coagulation temperature,
The coagulation temperature is preferably not higher than the maximum coagulation temperature from the viewpoint that the coagulated particles are likely to be large and coarse particles of 100 μm or more are easily generated.

The glass transition temperature of the polymer needed to determine the maximum coagulation temperature is 2-5 mm thick made by pressure forming the polymer,
It is obtained by measuring the dynamic viscoelasticity using a plate with a width of about 5 mm.

The lower limit of the coagulation temperature in step (I) is not particularly limited as long as it is at least the temperature at which the dispersion medium (water) of the slurry obtained in step (I) freezes. However, since the temperature of the polymer latex obtained by a practical emulsion polymerization method is 20 ° C. or higher, it is desirable to coagulate the polymer latex at 20 ° C. or higher which does not require cooling.

Further, in the step (I), it is desirable to coagulate particles having a particle diameter (hereinafter abbreviated as particle diameter) of 100 μm or more contained in the coagulated particles to 1% by weight or less. In particular, when granulating a powdery polymer as a product into fine powdery particles with an average particle size of 150 μm or less, coagulated particles with a particle size of 100 μm or more produce coarse powder in the powdery polymer, resulting in a particle size distribution. Widen
Since the controllability of the particle size is impaired, it is more preferably 0.5% by weight or less.

The weight fraction of coagulated particles with a particle size of 100 μm or more is obtained by filtering the coagulated slurry with a sieve having a mesh of 100 μm (a wire mesh of 150 mesh can be used) and filtering the coagulated particles remaining on the sieve. It can be determined from the weight measured by gently washing with 10 times the amount of tap water, followed by drying, and the weight measured by collecting particles that have passed through the sieve with filter paper and drying.

The time required for the coagulation in step (I) is very short, and as described above, the average residence time is usually 0.1 minutes to 1 hour, preferably 0.5 minutes to 10 minutes. If it is less than 0.1 minutes, coagulation will be incomplete and uncoagulated latex will flow into the step (II) and granulation tends to be unstable, which is not preferable. If it is set to 1 hour or more, the apparatus becomes excessively large, which is not preferable.

The organic liquid used in step (II) must be one that is sparingly soluble in water and does not dissolve the polymer contained in the polymer latex. Solubility of organic liquids in water is typically 0.5
It is desirable that the amount is not more than 0.1% by weight, more preferably not more than 0.1% by weight. The solubility here means a value measured at 20 ° C. An organic liquid having a solubility of more than 0.5% by weight has a small interfacial tension with water, and therefore the cohesive force based on the "liquid cross-linking force", which is almost proportional to the interfacial tension, becomes small. A liquid is required, which is not preferable. Further, when the solubility is high, the amount of the organic liquid dissolved in the aqueous phase increases, and the amount of the organic liquid adsorbed by the coagulated particles to generate the “liquid crosslinking force” decreases,
Furthermore, since large equipment is required to process the organic liquid dissolved in water, the solubility of the organic liquid in water is 0.
The amount is preferably 5% by weight or less, more preferably 0.1% by weight or less.

The ability of the organic liquid to dissolve the polymer cannot be quantitatively presented, but for convenience, the organic liquid can be selected by the following method. Target polymer is 1m in diameter
Granules of about m or pellets of about 1 mm on a side are placed in an organic liquid of 10 times the weight and stirred for about 1 hour. At this point, when the polymer is dissolved in the organic liquid to form a homogeneous phase and when the polymer is partially dissolved in the organic liquid and the viscosity of the organic liquid increases by 10% or more from its inherent viscosity, For polymers, the organic liquids cannot be used as organic liquids for carrying out the invention. further,
Even if the viscosity does not increase by 10% or more, the granular or pelletized polymer that is solid-liquid separated from the organic liquid is centrifugally dehydrated with 100 G of centrifugal force for 1 minute, and then the granular or pelletized polymer is fixed in a swelling state. However, even if the weight of the polymer increases by more than 10% from the initial weight, the organic liquid for the polymer cannot be used as an organic liquid for carrying out the present invention.

As described above, the organic liquid preferably used in the step (II) varies depending on the polymer to be used, but is, for example, paraffin hydrocarbon such as pentane, hexane, heptane, cyclopentane, cyclohexane, methylcyclo. Examples thereof include alicyclic hydrocarbons such as pentane and methylcyclohexane, and their alkyl-substituted products. These organic liquids can be used alone or in admixture of two or more.

The preferable amount of the organic liquid used is in the range of 20 to less than 60 parts by weight based on 100 parts by weight of the polymer in the polymer latex. If it is less than 20 parts by weight, the effect of granulating coagulated particles is reduced, fine powder is easily generated, and it becomes difficult to control the particle size distribution.

On the other hand, when the amount is 60 parts by weight or more, since a large amount of the organic liquid is present, the dispersion of the granulated particles becomes unstable, re-coalescence of the particles occurs, and coarse particles are easily generated. Further, a large amount of organic liquid has to be treated, which is disadvantageous in terms of energy cost.

The amount of the polymer in the polymer latex is obtained by coagulating the polymer latex with the above-mentioned coagulant, further raising the temperature and solidifying the resulting polymer, and drying the polymer to measure the weight of the polymer. be able to. The weight of the polymer obtained by such a method may include a polymerization aid such as an emulsifier or an initiator added during emulsion polymerization. In the present invention, since the polymer containing these emulsifiers and polymerization aids is granulated, the polymer obtained by the above-mentioned method as the polymer weight in the case of calculating the amount of the organic liquid or the weight ratio of the polymer in the whole mixture is calculated. Use weight. Such polymer weights are conventionally referred to as solids in the polymer.

The proportion of water in the total mixture of step (II) is 50-85% by weight,
More preferably, the range of 50 to 75% by weight is desirable. Further, the proportion of polymer in the total mixture is preferably in the range of 10 to 25% by weight.

If the water content of the entire mixture is less than 50% by weight, the apparent viscosity of the entire mixture will increase and coarse particles will tend to be generated. Furthermore, it becomes difficult to transfer a slurry in which a granulated polymer is dispersed in water (hereinafter, abbreviated as a granulated slurry) in an overflow form, and the apparatus becomes complicated. On the other hand, if the proportion of water in the total mixture exceeds 85% by weight, the bulk specific gravity of the resulting powdery granular polymer will decrease, and a large amount of water will have to be treated. There is.

A polymer content of less than 10% by weight in the total mixture has the same disadvantages as a water content of more than 85% by weight in the total mixture. The proportion of polymer in the total mixture is 25% by weight.
Above 10%, the same difficulties occur as when the proportion of water in the total mixture is less than 50% by weight.

In the step (II), after the organic liquid is continuously added, the mixture is held in the temperature (° C.) T range of the following formula for 0.5 minutes to 1 hour on average to granulate.

A-26 ≤ T ≤ A (In the formula, A represents the azeotropic temperature (° C) of the mixture liquid.) Here, the azeotropic temperature is the lowest temperature at which the mixture boils and is determined as follows. . The volatile constituents in the mixture are mainly two components, water and organic liquid, and these two constituents hardly dissolve each other, so that the total vapor pressures exhibited by them are given by the sum of the vapor pressures of the pure constituents. The temperature at which the total vapor pressure is equal to the total pressure on the liquid surface is the azeotropic temperature A of the mixture.

If the temperature T is lower than A-26 (° C), the granulation speed is remarkably slowed, and ungranulated fine powder is likely to be generated. On the other hand, when the temperature T exceeds the azeotropic point A (° C.) of the mixture, the mixture is boiled and stable stirring operation cannot be performed, so that coarse particles are generated and it becomes difficult to control the particle size distribution. Further, if the average granulation time is less than 0.5 minutes, granulation is insufficient and fine powder tends to be generated, and if it exceeds 1 hour, the granulator becomes excessively large, which is disadvantageous in terms of productivity.

In the step (II), a surfactant can be added to prevent the granulated particles from coarsening and to increase the flow stability of the slurry containing the granulated particles. As the surfactant, sodium alkyl sulfonate, sodium alkyl allyl sulfonate, sodium amide sulfonate,
Step (I): Anionic surfactant containing a sulfonic acid group such as sodium dialkylsulfosuccinate, sodium alkylbenzenesulfonate, sodium alkylnaphthalenesulfonate, and partially saponified polyvinyl alcohol
It is preferable that the coagulant used in 1. does not lose the surfactant effect.

In addition, the amount of surfactant used is 0.05-
It is 2% by weight, preferably 0.05 to 1.5% by weight.
When the amount used exceeds 2% by weight, the purity of the obtained polymer is lowered and the cost of the product is increased.
Not preferred.

The method of adding the surfactant is not particularly limited, and the surfactant is dissolved or dispersed in an organic liquid or water and added. In order to make the polymer particles thus continuously granulated more dense, the polymer particles are usually heated to a temperature not lower than the glass transition temperature of the polymer and subjected to heat treatment. Such processing is called solidification processing. The temperature of the solidification treatment depends on the glass transition temperature of the polymer, but is usually 60
~ 120 ℃, treatment time is 1 ~ 60
It's about a minute.

In the present invention, when the organic liquid is added to the slurry of coagulated particles and the coagulated particles are granulated by stirring or shaking, the interfacial tension between the dispersion medium of the slurry and the organic liquid is 0.5 to 30 dyne /
It is also possible to control the particle size of the obtained powdery granular polymer by controlling the particle size in cm, preferably in the range of 0.5 to 20 dyne / cm.

When the interfacial tension between the dispersion medium and the organic liquid is less than 0.5 dyne / cm, the liquid crosslinking force by the organic liquid is weakened, the particle size distribution of the obtained powdery granular polymer is broadened, the fine powder is increased, and the fluidity is deteriorated. It is not preferable. On the other hand, the interfacial tension is 30dy
When it exceeds ne / cm, the cohesive force due to the liquid bridging force becomes very large, and the coagulated particles are granulated too much and the diameter is 1c.
It grows up to about m particles, making stable granulation difficult. In particular, in the case of performing continuous granulation, there is a disadvantage that coarse particles grown to a size of about 1 cm are not discharged from the granulation layer and accumulate. Then, in the overflow type granulation tank (15) as shown in FIG. 1, coarse particles block the overflow line (20), which makes stable operation for a long time difficult. Therefore, the interfacial tension must be 30 dyne / cm or less, preferably 20 dyne / cm or less in order to avoid the above-mentioned instability of granulation.

The interfacial tension between the dispersion medium and the organic liquid is measured at 20 ° C by the following method. The coagulated particle slurry is filtered to separate the coagulated particles from the dispersion medium. The organic liquid and other additives were added to the dispersion medium at the same amount ratio and temperature as when granulating the mixture, and the mixture was gently stirred for about 1 minute and then allowed to stand to bring the interface between the dispersion medium phase and the organic liquid phase. Measure the interfacial tension.
A commercially available surface tensiometer can be used for measuring the interfacial tension. In the examples described below, the Kyowa CBVP surface tension meter from Kyowa Kagaku Co.
A3 type and glass plate were used.

When the interfacial tension between the dispersion medium and the organic liquid is less than 0.5 dyne / cm, the granulation effect of the organic liquid is weakened, which is not preferable.

The interfacial tension between the dispersion medium and the organic liquid can be controlled by adding a surfactant. As the surfactant, depending on the coagulant used for coagulating the polymer latex,
It is preferable that the surfactant effect is not lost. For example, the above-mentioned anionic surfactants containing sulfonic acid groups such as sodium alkylsulfonate, sodium alkylallylsulfonate, sodium amidosulfonate, sodium dialkylsulfosuccinate, sodium alkylbenzenesulfonate and sodium alkylnaphthalenesulfonate, and partially saponified polyvinyl. Alcohol or the like can be used.

The amount of the surfactant used is in the range of 0.05 to 2% by weight, preferably 0.05 to 1.5% by weight, based on the organic liquid, as described above. If the amount used exceeds 2.0% by weight, the purity of the obtained polymer is lowered and the cost of the product is increased, which is not preferable.

The method of adding the surfactant is not particularly limited, and the surfactant is dissolved or dispersed in an organic liquid or water and added.

Next, a typical apparatus used for carrying out the present invention will be described first.
This will be described with reference to the drawings.

The polymer latex is sent from the metering pump (1) to the coagulation tank (5) via the line (2). The coagulant is sent from the metering pump (3) to the coagulation tank (5) via the line (4). The coagulation tank (5) has a temperature control medium inlet / outlet port (7),
It is equipped with a jacket (9) with (8) and a stirrer (6). The polymer latex supplied here is coagulated with a coagulant. The coagulated latex becomes a slurry and is sent to the granulation tank (15) through the line (10) by overflow or pressure feeding, and is fed by the metering pump (11) through the line (12) to the organic liquid, And, if necessary, it is continuously mixed with water supplied through a line (14) by a metering pump (13) in a granulation tank (15) to granulate coagulated particles. The granulation tank (15) has a temperature control medium inlet / outlet port (16),
A jacket (19) having (17), a steam inlet (28) for heating, and an agitator (18) are provided. The granulated slurry is sent to the solidification tank (21) through the line (20) due to overflow, and is solidified, and at the same time, the organic liquid is azeotropically removed. The solidification tank (21) includes a temperature control medium inlet / outlet port (23), a jacket (25) having (24), an agitator (22), an organic liquid recovery condenser (26) and a steam injection line (29). I have it. The solidified slurry overflowed to the line (2
It is taken out from 7) and treated in a filtration, washing and drying process (not shown) to obtain a desired powdery granular polymer.

Hereinafter, the present invention will be described in more detail with reference to examples.
The examples were carried out using an apparatus as shown in FIG.

〔Example〕

Example 1 Methyl methacrylate obtained by emulsion polymerization method (85% by weight)
Copolymer latex of butyl acrylate (15% by weight) (solid content 27.8% by weight) and the coagulant of the kind shown in Table 1 in the coagulation tank (5 ) Was continuously supplied to the above) by metering pumps (1) and (3). The coagulation tank (5) had a cylindrical shape, and the stirrer (6) attached to it had a rotational speed of about
It was rotated at 700 rpm. The slurry after coagulation (slurry in which coagulated particles are dispersed in water; hereinafter abbreviated as “coagulation slurry”) overflows from the overflow port of the coagulation tank (5) and passes through the line (10) to the granulation tank. I entered (15).

At the same time when the coagulated slurry began to enter the granulation tank (15), the organic liquid and water were continuously supplied to the granulation tank (15) by the quantitative pumps (11) and (13). Further, the types and amounts of the surfactants shown in Table 1 were dissolved in the media shown in Table 1 and supplied to the granulating tank (15). The granulating tank (15) had a cylindrical shape, and the attached stirrer (18) was rotated at a rotation speed of 500 rpm. The granulated slurry overflowed from the coagulation tank (15) and entered the solidification tank (21) via the line (20). About 8 hours after the slurry started to overflow from the solidification tank (21), about 1 slurry sample was collected, dehydrated, washed, and dried to obtain a granular polymer. The bulk specific gravity, average particle diameter, particle size distribution, and particle uniformity of the obtained powdery granular polymer were measured.

Bulk specific gravity is measured according to JIS K-6721 and fluidity is measured according to JIS K-
The granules were put into the bulk specific gravity measuring machine used in 6721, and the outflow state when the damper was removed was observed, and its fluidity was judged according to the following criteria.

Outflow condition ○: The sample spontaneously flows out when the damper is removed ×: It flows out when a shock is continuously applied XX: It does not flow out even when a shock is continuously applied. Also, the average particle diameter D ₅₀ is the median diameter on a weight basis. That is.

Further, the degree of particle uniformity N is expressed by the following formula N = D ₇₅ / D ₂₅ (where D ₇₅ is the particle size at 75% of the cumulative weight distribution curve (μ
m) The D ₂₅ represents a particle size in the 25% of the cumulative weight distribution curve of the particles ([mu] m). ). These measuring methods are common to the following examples and comparative examples. The measurement results are shown in Table 1. The organic liquid used was n-hexane, and the azeotropic temperature A with water was about 61.
° C. A powdery polymer having a sharp particle size distribution and a small amount of fine particles of 37 μm or less and good flowability was obtained.

Example 2 A powdery polymer was obtained in the same manner as in Example 1 under the conditions shown in Table 1. The amount of fine powder is small, and the uniformity of particles is 2.
A powdery granular polymer having a sharp particle size distribution of 5 or less, ie 2.2, and having good fluidity was obtained.

Example 3 A powdery polymer was obtained in the same manner as in Example 1 under the conditions shown in Table 1. Since n-heptane is used as the organic liquid, the azeotropic temperature A with water is about 79 ° C. The amount of fine powder was small, the particle uniformity was 1.9, the particle size distribution was sharp, and a powdery polymer with good fluidity was obtained.

Comparative Example 1 A powdery granular polymer was obtained in the same manner as in Example 1 under the conditions shown in Table 1. However, since the temperature T of the mixture in the granulation tank was out of the predetermined range, only a granular polymer containing a large amount of coarse particles of 850 μm or more and having a large particle uniformity ratio of 3.0 and poor fluidity was obtained.

Comparative Example 2 A powdery granular polymer was obtained in the same manner as in Example 1 under the conditions shown in Table 1. However, since the mixture temperature T in the granulation tank is higher than the azeotropic temperature, azeotropy occurs in the granulation tank and stable stirring operation in the tank cannot be performed, and the particle uniformity ratio N is as large as 3.1 and 850 μm or more. Only a granular polymer containing a large amount of coarse particles and having poor fluidity was obtained.

Examples 4 to 6 In the same manner as in Example 1 except that the volume of the granulation tank was changed in order to change the residence time of the mixture in the granulation tank, the powdery and granular polymer was prepared under the conditions shown in Table 2. Obtained. Since the average residence time of the mixture in the granulation tank was within the predetermined range, the amount of fine powder was small and the particle uniformity was 2.5 or less, the particle size distribution was sharp, and a powdery polymer with good fluidity was obtained. .

Comparative Example 3 A granular polymer was obtained under the conditions shown in Table 2 in the same manner as in Example 1 except that the average residence time in the granulation tank was further shortened. Since the average residence time of the mixture in the granulation tank was out of the predetermined range, the amount of fine powder was large, and the uniformity of the particles was 2.5 or more, and only a powdery polymer having poor fluidity was obtained.

Examples 7 and 8 Two kinds of sodium dioctyl sulfosuccinate and sodium dodecylbenzene sulfonate, which are anionic surfactants and have a sulfonic acid group in the molecule, are used as the surfactants under the conditions shown in Table 3. A powdery granular polymer was obtained in the same manner as in Example 1.

A powdery granular polymer having a small amount of fine powder and a particle uniformity of 2.5 or less, a sharp particle size distribution and good fluidity was obtained.

Example 9 A powdery granular polymer was obtained in the same manner as in Example 1 under the conditions shown in Table 3 using polyvinyl alcohol having a degree of polymerization of about 500 as a surfactant.

A powdery polymer having a fine particle size distribution and a sharp particle size distribution and good fluidity was obtained with a small amount of fine powder and a particle uniformity ratio of 2.5 or less.

Reference Examples 1 to 5 Under the conditions shown in Table 4, powdery granular polymers were obtained in the same manner as in Example 1. A fine-grained polymer having a small particle size and a particle size distribution of 2.5 or less and a sharp particle size distribution and good fluidity was obtained. Further, the bulk specific gravity increased as the weight ratio of water to the total mixture decreased, and the bulk specific gravity could be controlled.

Comparative Example 4 The same operation as in Example 1 was performed under the conditions shown in Table 4. About 10 minutes after the slurry was discharged from the discharge line (20) of the granulation tank (15), the line (20) was closed and the slurry was mixed because the mixing ratio of water in the total mixture in the granulation tank (15) was small. It is no longer discharged to the solidification tank.

Example 10 and Reference Example 6 The amount of the organic liquid used was 10% of the solid content in the polymer latex.
20 parts by weight and 100 parts by weight relative to 0 parts by weight were used to obtain a powdery granular polymer in the same manner as in Example 1 under the conditions shown in Table 5. A fine-grained polymer having a small particle size distribution and a particle size distribution of 2.5 or less with a sharp particle size distribution and good fluidity was obtained.

Comparative Example 5 A granular polymer was obtained in the same manner as in Example 1 under the conditions shown in Table 5 without using any organic liquid. Only a granular polymer with a large amount of fine powder, a large particle uniformity ratio of 3.2, a wide particle size distribution, and poor fluidity was obtained.

Comparative Example 6 The amount of organic liquid used was 10% solids in the polymer latex.
A powdery polymer was obtained in the same manner as in Example 1 under the conditions shown in Table 5 with 0 parts by weight being 10 parts by weight. Only a granular polymer with a large amount of fine powder, a large particle uniformity ratio of 3.2, a wide particle size distribution, and poor fluidity was obtained.

Comparative Example 7 The amount of organic liquid used was 10% solids in the polymer latex.
A powdery granular polymer was obtained in the same manner as in Example 1 under the conditions shown in Table 5 with 180 parts by weight relative to 0 parts by weight. Although the amount of fine powder was small, the uniformity of the particles was 3.5, which was bad and contained only a large amount of coarse particles of 850 μm or more, so that only a granular polymer having poor fluidity was obtained.

Example 11 A powdery polymer was obtained in the same manner as in Example 1 under the conditions shown in Table 6 with the stirring rotation speed of the coagulation tank set to 1200 rpm and the stirring rotation speed of the granulation tank set to 1200 rpm. A granular polymer having a particle size distribution of 2.5 or less and a sharp particle size distribution and good fluidity was obtained.

Examples 12 to 14 Powdered and granular polymers were obtained in the same manner as in Example 11 under the conditions shown in Table 7. The higher the weight fraction of polymer in the total mixture in the granulation tank, the higher the bulk specific gravity.

Comparative Example 8 A powdery granular polymer was obtained in the same manner as in Examples 12 to 14 except that the weight ratio of the polymer to the total mixture in the granulation tank was as low as 8%, but the bulk specific gravity was extremely low.

Examples 15 to 17 A copolymer latex of methyl methacrylate (90% by weight) and butyl acrylate (10% by weight) (solid content 27.8% by weight) was used and the same procedure as in Example 1 was carried out under the conditions shown in Table 8. To obtain a granular polymer. The uniformity of the particles was 2.5 or less, and the particle size distribution was sharp and the fluidity was good.

Comparative Example 9 A granular polymer was produced in the same manner as in Example 3, except that the temperature in the granulation tank was changed to 45 ° C. The evaluation results are shown in Table 8.

Examples 18 to 21 Methyl methacrylate obtained by emulsion polymerization method (85% by weight)
Copolymer latex of styrene and butyl acrylate (15 wt%) (solid content 27.8%) and coagulant of the type shown in Table 9 at the supply amount shown in Table 9 in the coagulation tank (5) Was continuously supplied to the container by the metering pumps (1) and (3). The coagulation tank (5) had a cylindrical shape, and the stirrer (6) attached to it had a rotational speed of 70
It was rotated at 0 rpm. The coagulation slurry overflowed from the overflow port of the coagulation tank (5) and entered the granulation tank (15) via the line (10).

As soon as the coagulated slurry begins to enter the granulation tank (15),
The organic liquid and water were supplied to the granulation tank (15) by the metering pumps (11) and (13). Further, the kinds and amounts of the surfactants shown in Table 9 were dissolved in the media shown in Table 9 and supplied to the granulation tank (15). The granulating tank (15) had a cylindrical shape, and the attached stirrer (18) rotated at a rotation speed of 500 rpm.

The granulated slurry overflowed from the coagulation tank (5) and entered the solidification tank (21) through the line (20). Eight hours after the slurry began to overflow from the solidification tank (21), about 1 slurry sample was taken and dehydrated,
It was washed and dried to obtain a powdery polymer. The bulk specific gravity, the average particle size, the particle distribution, and the uniformity of the particles of the obtained powdery granular polymer were measured.

In addition, the interfacial tension between the dispersion medium and the organic liquid was determined by adding water to the dispersion medium obtained by solid-liquid separation of the slurry overflowing from the coagulation tank (5) so that the same amount ratio and temperature as during granulation were obtained. The mixture containing the surfactant and the organic liquid was placed in a closed container, stirred for 1 minute and then left to stand, transferred to a Petri dish for measuring interfacial tension, and manufactured by Kyowa Kagaku Co., Ltd. Kyowa CB.
Using VP type surface tension meter A3 type and glass measuring plate,
It was measured. The method for measuring the interfacial tension is common to the following examples and comparative examples. Table 9 shows the measurement results. A fine-grained polymer having a small amount of fine powder and a particle size distribution of 2.5 or less and a sharp particle size distribution and good fluidity was obtained. Further, the average particle diameter decreased as the polymerization ratio of the surfactant to the organic liquid increased, and the average particle diameter could be controlled.

Reference Example 7 A granular polymer was obtained from the same copolymer latex as in Example 27 by the same method as in Example 21, except that the amount of the surfactant added was increased to the amount shown in Table 9. The average particle size of the obtained powdery polymer was lower than that of Example 27, but the amount of the surfactant added was large and the interfacial tension between the dispersion medium and the organic liquid (n-heptane) was too low. The degree was 2.9 and the particle size distribution was wide, and the amount of fine powder of 37 μm or less was extremely large.

Reference Example 8 An attempt was made to obtain a powdery granular polymer by using the same copolymer latex as in Example 24 in the same manner as in Example 18 except that the surfactant was not used. However, since the interfacial tension between the dispersion medium and the organic liquid (n-heptane) is too large, coarse particles accumulate in the granulation tank and the overflow line (20) is blocked after about 10 minutes, and stable granulation operation is possible. I couldn't.

Examples 22 to 24 Using a copolymer latex of methyl methacrylate (80% by weight) and butyl acrylate (20% by weight) (solid content 27.8% by weight), a stirrer for coagulation tank (5) and granulation tank (15) Number of rotations (number of rotations of stirrer (6) and stirrer (18))
Except that the speed was 1200 rpm, the same procedure as in Example 18 was repeated.
A powdery polymer was obtained under the conditions shown in Table 0.

A finely divided powdery polymer having a sharp particle size distribution and good fluidity was obtained. Further, as the amount of the surfactant added increased, the average particle size became smaller, and it was possible to control the particle size.

Examples 25 to 27 A polymer latex obtained by graft-polymerizing 15 parts by weight of methyl methacrylate and 25 parts by weight of styrene to 60 parts by weight of a rubber polymer having a composition of butadiene (75% by weight) and styrene (25% by weight) was used. In the same manner as in Example 28,
Granulation was performed according to the conditions in the table to obtain a powdery polymer.

A powdery polymer having a small amount of fine powder and a sharp particle size distribution and good fluidity was obtained. Moreover, the average particle diameter decreased as the amount of the surfactant added increased, and the particle diameter could be controlled.

According to the method for producing a granular polymer of the present invention, a granular polymer having a small amount of fine powder, a sharp particle size distribution, and a controlled bulk specific gravity can be obtained. Further, since the organic liquid used is sparingly soluble in water and the amount used is small, the device can be small, and the running cost required for recovering the organic solvent is very small. According to the present invention, the polymer obtained by the emulsion polymerization method can be granulated economically. Further, it has an excellent effect such that the particle size of a powdery polymer having a small amount of fine powder and a sharp particle size distribution can be arbitrarily controlled, and a powdery polymer having a particle size most suitable for the application can be obtained. .

Claims (5)

(57) [Claims] 1. A continuous process for producing a powdery or granular polymer, which comprises successively treating a polymer latex obtained by an emulsion polymerization method in the following step (I) and step (II). Step (I): A step of coagulating the polymer latex to form a slurry in which coagulated particles are dispersed in water. Step (II): The slurry obtained in Step (I), an organic liquid that is sparingly soluble in water and does not dissolve the polymer, and, if desired, a necessary amount of water in the following (a) to (c) are added. A step of continuously mixing and granulating under conditions. (A): The proportion of water in the total mixture is 50 to 85% by weight. (B): 20 parts by weight to less than 60 parts by weight of the organic liquid with respect to 100 parts by weight of the polymer in the polymer latex. (C): The temperature (° C.) T of all the mixtures is averaged within 0.5 minutes in the range of the following formula A-26 ≦ T ≦ A (where A represents the azeotropic temperature (° C.) of the mixture liquid). Hold for 1 hour. 2. In the step (II), an anionic surfactant containing a sulfonic acid group and / or polyvinyl alcohol is added in the molecule in an amount of 0.05 to 2% by weight based on the organic liquid, and after granulation, The continuous production method according to claim 1, wherein the granulated polymer particles are solidified. 3. The step (I) is carried out under the following conditions (d) and (e), and (d): the coagulation temperature is 10 ° C. or higher than the glass transition temperature of the polymer in the polymer latex. Low temperature. (E): Among coagulated particles, the proportion of particles having a particle diameter of 100 μm or more is 1% by weight or less. The continuous production method according to claim 1 or 2, wherein the proportion of the polymer in the total mixture is 10 to 30% by weight in the step (II). 4. The continuous production method according to claim 1, 2 or 3, wherein the organic liquid to be added is a paraffinic hydrocarbon or an alicyclic hydrocarbon and an alkyl-substituted product thereof. 5. The continuous production method according to claim 1, 2, 3 or 4, wherein the interfacial tension between the dispersion medium of the coagulated slurry and the organic liquid is in the range of 0.5 to 30 dyne / cm.