JP4080782B2 - Method for producing bead polymer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a bead polymer efficiently and stably.
[0002]
[Prior art]
The suspension polymerization method is a production technique particularly useful as a polymerization method for vinyl monomers. The bead polymer can be obtained from the slurry after suspension polymerization, and is used for applications such as paint raw materials, ink raw materials, binders for copying machine toners, binders for ceramic firing, intermediate materials for thermoplastic resins, and the like. Yes.
[0003]
Most of these bead polymers are manufactured through processes such as slurry dehydration, washing, and drying. The type of equipment used in each process following the polymerization process depends on product quality, manufacturing cost, and consumption. May have a significant impact on energy and waste. In other words, the optimization of the equipment to be used is an important production technology issue.
[0004]
Examples of the dryer that can be used industrially in the drying process of the slurry dehydrated product during the production of the bead-shaped polymer include those that are heated by drying under reduced pressure, and those that are heated under reduced pressure in the vertical direction. What is performed in a container that can be rotated, is dried while the bead polymer is air-fed in the tube using warm air, and warm air is blown from the lower side of the one-stage perforated plate to beside the bead polymer on the upper side. Conventionally, what performs drying while flowing in a direction is known.
[0005]
[Problems to be solved by the invention]
However, the thing which dries by heating under reduced pressure, or the thing which dries in the container which can be dried in the vertical direction after heating under reduced pressure, it takes a long time to obtain a sufficient drying effect However, it is difficult to dry and remove the water present in the bead polymer by drying the bead polymer using the warm air while air transporting in the tube. Had.
The one that blows warm air from the lower side of the first stage perforated plate and causes the bead polymer to flow in the lateral direction on the upper side is the most productive dryer among these, Since there is a restriction that the air flow rate cannot be increased so much in structure, it has been difficult to obtain a sufficiently satisfactory drying efficiency.
[0006]
An object of the present invention is to provide a method for producing a bead polymer efficiently and stably by selecting a dryer suitable for the production of the bead polymer.
[0007]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that a two-stage fluidized bed dryer having a primary drying chamber and a secondary drying chamber arranged above and below solves the above problems, and has completed the present invention.
[0008]
That is, the present invention has a slurry dehydration drying process using a two-stage fluidized bed dryer in which a primary drying chamber and a secondary drying chamber are arranged up and down, and the temperature rise in the secondary drying chamber is high. The present invention relates to a method for producing a bead-like vinyl polymer that terminates the secondary drying process of each drying batch when a set value is reached .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
As a constituent of the bead polymer obtained by the present invention, a monomer having an alkenyl group can be used. For example, vinyl chloride, styrene, divinylbenzene, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl. Examples include, but are not limited to, acrylate, methyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, methacrylic acid, and 2-hydroxyethyl methacrylate.
[0010]
This bead-like polymer is particularly preferably produced by suspension polymerization, and usually has a bead-like shape close to a true sphere. Although there is a distribution in the bead particle size, the particle size in weight average is usually in the range of 10 to 1000 μm.
[0011]
Suspension polymerization can be carried out in a vessel having a polymerization temperature control function and a stirring function using the above-mentioned monomers selected according to the purpose, a polymerization aid and water.
Polymerization aids include 2,2'-azobisisobutyronitrile, polymerization initiators that are radical sources such as benzoyl peroxide, chain transfer agents such as n-dodecyl mercaptan, α-methylstyrene dimer, polyvinyl alcohol , Dispersing agents such as potassium methacrylate-methyl methacrylate copolymer (surfactants for the purpose of stabilizing the dispersion of monomers in water), dispersing aids such as sodium sulfate and manganese sulfate, etc. can do.
[0012]
The bead polymer can be obtained by dehydrating the slurry obtained by suspension polymerization using a dehydrator and then drying. The production of a bead polymer by suspension polymerization is usually a batch operation using a polymerization kettle, but in the present invention, for the purpose of continuously producing a bead polymer, the polymerization kettle is used. A tank for temporary storage of the slurry can be provided between the separator and the dehydrator.
By using this temporary storage tank, the slurry can be continuously fed into the dehydrator, and the dehydration process can be operated under more stable conditions.
[0013]
When the slurry is continuously supplied from the temporary storage tank to the dehydrator, a slurry circulation line having a branch line connected to the dehydrator is installed in the temporary storage tank, and the slurry is supplied to the circulation line by a pump. preferable. By installing an automatic flow control valve in the branch line and adjusting its opening, the supply rate of slurry to the dehydrator can be controlled. In this case, the slurry that did not flow from the circulation line to the branch line is returned to the temporary storage tank.
[0014]
Various dehydrators can be used for dehydrating the slurry. For example, a mechanism that squeezes water using centrifugal force, a mechanism that separates water from specific gravity by applying the principle of centrifugal sedimentation, and a mechanism that sucks and removes water on a perforated belt are appropriately selected. Can be used.
[0015]
The bead polymer after the dehydration step can be dried as it is, but the bead polymer can be washed before drying. By washing, the purity of the bead polymer can be increased.
[0016]
As a washing method of the bead polymer, for example, a method of adding water to the bead polymer and making it slurry again and stirring and mixing in the tank, after dehydration of the bead polymer in a dehydrator having a washing function The method of washing with water, the method of combining both of these, etc. can be mentioned. The washed bead polymer can be dehydrated again before drying.
[0017]
The bead polymer obtained through the dehydration process tends to further improve the handleability as a product through the drying process. Even after the dehydration step, water remains on the surface of the bead polymer, and the inside of the bead polymer is close to saturated water absorption, so that the water content of the bead polymer is further reduced. Requires a drying step.
[0018]
In the present invention, a two-stage fluidized bed dryer in which a primary drying chamber and a secondary drying chamber are arranged up and down is used in the drying process.
This is because the use of a two-stage fluidized bed dryer makes it possible to continuously perform the drying process and to efficiently and stably produce a bead-like polymer for a long period of time. .
[0019]
As the above-mentioned dryer, those known as a semi-continuous two-stage fluidized bed dryer can be used. For example, commercially available products such as an inverted bed batch type fluidized bed dryer (B-FBD-R type, manufactured by Nara Machinery Co., Ltd.) can be used.
The main body part of the dryer used in the present invention is vertically long and divided into three in the vertical direction. From the upper side, the primary drying chamber, the secondary drying chamber, and the lowermost side serve as a temporary storage chamber for the dried bead polymer. It has the function of Each of the three divided chambers is partitioned by a perforated plate that can rotate, and these plates are hereinafter referred to as an upper bed and a lower bed.
Here, it is not preferable to have three or more drying chambers because the operation management tends to be complicated while the contribution to productivity improvement is small.
[0020]
The dehydrated bead polymer is first fed into the primary drying chamber. The bead polymer may be supplied continuously or intermittently. The equipment for supplying the bead polymer is not particularly limited. For example, air transportation using airflow drying pipe equipment can also be performed. Further, when the dehydrator is disposed above the dryer, the dehydrated bead polymer can be dropped and supplied.
[0021]
The bead-shaped polymer fed into the primary drying chamber undergoes a first drying (primary drying) process. Subsequently, the primary dried bead polymer falls into the secondary drying chamber by the rotation of the upper bed and is subjected to a second drying (secondary drying) treatment. With such an operation method, each time the upper bed rotates, a specific amount of bead polymer falls into the secondary drying chamber, and this specific amount of bead polymer is hereinafter referred to as a dry batch. While one batch of dried beads is subjected to the secondary drying process in the secondary drying chamber, the primary drying process of the beads to be the next drying batch proceeds in the primary drying chamber.
[0022]
One batch of the dried beads after the drying process up to the secondary drying chamber falls into the temporary storage chamber of the bead polymer on the lowest floor by the rotation of the lower bed. Regarding the relationship between the rotation timings of the two upper and lower beds, it is preferable that the upper bed is rotated soon after the lower bed is rotated because continuous drying operation with high productivity is possible. The temporary storage chamber for the dried bead-like polymer is preferably a conical shape with the lower side deflated. By doing so, the bead polymer after the drying process is accumulated from the lowermost part of the temporary storage chamber, so by installing a discharge facility at the lowermost part, it is possible to proceed to the next step at a predetermined speed of the bead polymer. This is because it becomes easier to supply. By using the above operation method, each drying batch can pass through a drying process continuously.
[0023]
In the two-stage fluidized bed dryer used in the present invention, the drying air is taken from the upper part of the temporary storage chamber of the dried bead polymer. The drying air is prepared through piping through a device appropriately selected from a filter for removing foreign substances, a blower for blowing air, an air volume control valve, an air heater, a dehumidifier, a humidifier, etc., as necessary. The atmosphere in the dryer can be controlled by the drying air. The drying air taken in from the temporary storage room is blown from the temporary storage room through the lower bed, which can be called the ceiling, into the secondary drying room, and the bead polymer on the perforated plate is allowed to flow, thereby drying efficiency. High drying operation can be performed. The drying air further blows up into the primary drying chamber through the upper bed, which can be said to be the ceiling of the secondary drying chamber, and contributes to the drying of the bead polymer on the perforated plate.
[0024]
On the upper side of the primary drying chamber, using the difference in specific gravity between the bead polymer and air, only the bead polymer is collected and the air is discharged out of the system. It is preferable to install a cyclone tower. This is because by installing a cyclone tower, drying can be performed with a very large air flow rate.
[0025]
In the present invention, the secondary drying process for each batch is terminated when the temperature rise in the secondary drying chamber reaches the set condition .
This is because the moisture content (water content) of the bead polymer, which is one of important quality control items, tends to be stably maintained within a predetermined range.
[0026]
For example, it is possible to stably maintain the moisture content within a predetermined range by setting two conditions of drying temperature and drying time in the dryer to appropriate constant conditions and performing continuous operation. For this purpose, it is required that the amount and particle size distribution of the bead polymer fed into the drying process, and the flow rate and absolute humidity of the drying air be stably maintained within a certain range.
[0027]
However, in practice, it is difficult to keep the bead polymer obtained by the suspension polymerization method in a stable and stable quantity and quality, and the absolute humidity in the drying air is the temperature of the atmosphere to be taken in.・ Because it is affected by changes in humidity, it is difficult to keep it stable. That is, it is difficult to keep the water content of the bead polymer stably within a predetermined range for a long period of time simply by setting the drying temperature and drying time.
[0028]
An example of a preferable operation method of the drying step in the present invention is shown below.
In several batches from the first batch immediately after the start of the drying process operation, the two-stage fluidized bed dryer is operated with the drying temperature and drying time set to constant conditions.
For example, when the bead polymer starts to accumulate in the primary drying chamber, the drying timer starts to run, and when the set time is reached, the lower bed first rotates, and after the rotation ends and returns to its original state, the upper bed Rotate. Due to the rotation of the upper bed, the dried first batch of bead polymer falls into the secondary drying chamber. Thereafter, when the upper bed returns to the original state, the drying timer is reset and starts again. This time point will be referred to as the second drying process start point of the first drying batch for convenience. From the start of the secondary drying process of the first batch of drying, the bead-shaped polymer that becomes the second batch of drying begins to accumulate in the primary drying chamber. When the drying timer set time is reached, first, the beads of the first batch of drying in the secondary drying chamber fall into the temporary storage chamber of the dried bead-like polymer this time due to the rotation of the lower bed. This time is called the end of the secondary drying process for the first drying bed. Then, due to the subsequent rotation of the upper bed, the second drying second batch falls into the secondary drying chamber, and when the upper bed returns, the next drying timer starts, and the first drying chamber contains the third drying batch. The bead polymer that begins to accumulate begins to accumulate.
[0029]
While this operation is continued for several drying batches, the drying temperature and drying time for determining the water content of the bead polymer taken out from the temporary storage chamber to a preferable value are determined. Subsequently, in the drying operation at the determined drying temperature / drying time, the degree of increase in the secondary drying room thermometer instruction value from the secondary drying process start time to the end of the secondary drying process is confirmed.
Then, the operating condition of the two-stage fluidized bed dryer is changed to a condition that the secondary drying process of each batch is terminated when the temperature rise in the secondary drying chamber reaches a set value . When the confirmed temperature rise is input as a set value, the lower bed rotates from the subsequent drying batch when the temperature rise of the secondary drying chamber reaches the set value instead of the drying time. A series of drying batch update operations is continued.
After that, until the production of the one product is completed, the drying process can be performed continuously for a long time under stable conditions with high productivity without changing any of the operating conditions set in the drying process. A product with a moisture content can be obtained.
[0030]
The dried bead polymer may be passed through a sieving device for the purpose of taking out particles having a particle size suitable for the purpose. Even in this step, stable operation with good productivity can be achieved by the effect of the present invention. It becomes possible.
[0031]
The bead polymer obtained in the present invention can be used for applications such as paint raw materials, ink raw materials, binders for copying machine toners, binders for ceramic firing, etc. It can also be used for resin molding material applications.
[0032]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention and its effect are demonstrated concretely, this invention is not limited by these. In addition, the physical property evaluation of the bead-shaped polymer obtained by the Example was implemented based on the method of following [1]-[2].
[0033]
[1] Moisture content Measured by a method based on the moisture vaporization method of Section 4.5 of JIS K 0068 “Karl Fischer titration method”.
[0034]
[2] A weight average particle size bead-shaped polymer was dispersed in water and measured using a laser diffraction / scattering particle size distribution analyzer [LA-910, manufactured by Horiba, Ltd.].
[0035]
( Reference Example 1 )
Uniformly distribute 100 parts by weight of methyl methacrylate, 0.1 part by weight of 2,2'-azobisisobutyronitrile and 0.3 part by weight of n-dodecyl mercaptan into a polymerization vessel for producing a polymer by suspension polymerization. Uniformly dissolve the dissolved polymerization raw material and 1 part by weight of sodium methacrylate-methyl methacrylate 7: 3 copolymer in advance, 0.01 part by weight of manganese sulfate and 0.1 part by weight of hydrogen peroxide (pure 35%). Then, 200 parts by mass of pure water was charged, and after substituting with nitrogen with stirring, polymerization was performed at 70 ° C., and after the peak of polymerization exotherm was detected, polymerization was further performed at 100 ° C. for 1 hour. After the polymerization, the inside of the kettle was cooled to room temperature, and the entire amount of the produced slurry was transferred to a slurry temporary storage tank.
Subsequently, the slurry is allowed to pass through successive steps of dehydration, washing, and second dehydration that are continuously operated under certain set conditions, and the resulting slurry dehydrated is continuously fed to the primary drying chamber and the secondary drying chamber. Set drying temperature 45 ° C, set secondary drying processing time (from the end of upper bed rotation to the start of lower bed rotation) 16 minutes while sending into the two-stage fluidized bed dryer with the drying chamber arranged vertically Drying operation was performed at an air flow rate of 3000 Nm ³ / hr. The water content of the bead polymer collected at the beginning of production is 0.42% and the weight average particle diameter is 100 μm. The water content of the bead polymer collected at the end of operation is 0.40% and the weight average particle diameter is It was 100 μm, and it was confirmed that the quality stability of the continuously produced bead polymer was excellent.
[0036]
( Reference Example 2 )
The same polymerization operation as in Reference Example 1 was continued 20 times. While the resulting slurry is sequentially transferred to a temporary slurry storage tank, all subsequent operations from dehydration, washing, second dehydration to two-stage fluidized bed dryer can be produced under the same operating conditions as in Reference Example 1. Continued until finished. It was possible to continuously produce a bead-like polymer while maintaining high productivity without causing any trouble on the way.
The water content of the bead polymer collected at the beginning of production is 0.40% and the weight average particle diameter is 100 μm. The water content of the bead polymer collected at the end of operation is 0.21% and the weight average particle diameter is It was 100 μm. Some variation was observed in the quality of the bead polymer, but it was confirmed to be at a practical level.
[0037]
( Example 1 )
The same polymerization operation as in Reference Example 1 and Reference Example 2 was carried out 20 times in the same manner as in Reference Example 2 . Except for the operation method of the two-stage fluidized bed dryer, all the steps were continued under the same set operating conditions as in Reference Example 1 and Reference Example 2 until the production was completed.
The operation method of the two-stage fluid dryer is as follows. From the drying start to fifth drying batched falls into the drying beads temporary storage chamber, Reference Example 1, Reference Example 2 and setting the drying temperature 45 ° C. is the same, set the drying time 16 minutes, setting the dry air flow rate 3000 Nm ³ / Drying operation was performed in hr. The water content of the product obtained in the fourth dry batch during this operation period was 0.42%, and the weight average particle size was 100 μm. And the temperature in the secondary drying chamber in the set secondary drying time of 16 minutes at this time rose by 7.5 ° C. Therefore, after the drying in the secondary drying chamber of the sixth batch of drying, instead of the drying time setting method, the temperature rise in the secondary drying chamber from the end of the upper bed rotation, which is the start time of the drying timer of each batch, is 7 When the temperature reached 5 ° C., the drying operation was started by the temperature difference setting method in which the rotation of the lower bed started, and thereafter, the drying operation method and the setting conditions were continued until the production was completed. It was possible to continuously produce a bead-like polymer while maintaining high productivity without causing any trouble on the way.
The water content of the bead polymer collected at the middle stage of production is 0.41% and the weight average particle diameter is 100 μm. The water content of the bead polymer collected at the end of operation is 0.37% and the weight average particle diameter is It was 100 μm, and it was confirmed that the quality stability of the continuously produced bead polymer was excellent over a long period of time.
[0038]
【The invention's effect】
According to the present invention, a bead polymer can be produced efficiently and stably over a long period of time, which is very useful industrially.

Claims (3)

When the slurry drying process is performed using a two-stage fluidized bed dryer with the primary drying chamber and the secondary drying chamber arranged one above the other, when the temperature rise in the secondary drying chamber reaches the set value The method for producing a bead-shaped vinyl polymer, in which the secondary drying treatment of each drying batch is completed.   The method for producing a bead-like vinyl polymer according to claim 1, wherein the slurry is obtained by a suspension polymerization method using water as a dispersion medium.   The method for producing a bead-like vinyl polymer according to claim 1 or 2, wherein each drying batch continuously passes through a drying step.