JPS61143403A - Method of removing high-boiling point organic compound - Google Patents

Abstract

PURPOSE:To remove effectively a high-boiling point organic compound such as an unreacted monomer, etc., remaining in a polymer without damaging powder characteristics and processing properties, by contacting slurry of the polymer having floating properties with a noncondensible gas at high temperature under strong stirring by a stirrer. CONSTITUTION:Slurry having preferably 8-20 wt.% concentration of a polymer (e.g., ABS resin, MBS resin, AS resin, etc.) having floating properties is brought into contact with a noncondensible gas (e.g., N2 gas, He gas, etc.) while being stirred strongly by a stirrer at high temperature under conditions of usually at 75-85 deg.C and at 10<5>-10<8> stirring Reynolds number, and a high-boiling poist organic compound which is an unreacted monomer having preferably >=100 deg.C boiling point is removed. USE:For example, when MBS resin is used as a food packaging material, a remaining styrene monomer can be effectively removed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for removing high-boiling organic compounds such as unreacted monomers remaining in a polymer that floats in an aqueous medium in a slurry state. Regarding.

(Prior art) A latex-like polymer obtained by emulsion polymerization is generally coagulated by contacting with an acid or salt, heat-treated, and then
It is obtained as a powder through dehydration and drying processes. Therefore, it is unavoidable that substances added during emulsion polymerization, decomposition products and side reaction products produced during polymerization, and polymers that remain unreacted are mixed into products as contaminants in normal processes. sea bream.

These contaminants not only adversely affect various processing properties of the polymer, but also often cause the polymer to become colored or have an odor, or to reduce the stability of the polymer. In addition, it not only reduces the operational stability during production and the 11iI of the product, but also causes not only odor but also health problems when the polymer is used as a food packaging material. .

In order to remove high-boiling organic compounds such as unreacted monomers with a boiling point of 100°C or higher, as well as residual unreacted monomers with a low boiling point, vacuum treatment of latex, Commonly attempted methods include gas-liquid contact treatment, steam stripping of slurry, and removal by drying. However, although there are various methods for removing residual monomers from suspension polymerization slurry in polymerization systems such as monomer chloride, which is a low-boiling monomer, Removal of residual monomers, etc. is considered impossible for the following reasons.

That is, removal from latex is not very advantageous due to problems such as foaming and scale generation, and steam stripping of slurries is generally uneconomical as it requires large amounts of steam and is exposed to steam for long periods of time. Therefore, an adverse effect on quality cannot be avoided, and removal by drying may cause a fire, and quality deterioration due to oxidation cannot be avoided.

For example, a butadiene polymer 1 consisting of 0 to 50% styrene (by weight, the same applies hereinafter) and 50 to 100% butadiene.
One or more monomers selected from vinyl aromatics, methacrylic esters, acrylic esters, and vinyl cyanide compounds in the presence of 0 to 90 parts (juho part, same hereinafter), 10-9 so that the total number of copies is 100 copies
In the case of HBS resin, which is a 0-part polymerized graft copolymer, it is restricted to completely terminate the polymerization reaction from the viewpoint of ensuring processing properties and quality, and the amount of unreacted monomer is 1000 ppl (vs. In some cases, it is unavoidable that the resin remains in high concentrations.

When such HBS resin is used as a food packaging material, it is essential to remove residual high-boiling organic compounds such as unreacted monomers. This is because, for example, when producing HBS A4 fat as a material for food packaging, residual styrene monomer is
This is because it is strongly desired to remove the amount below.

[Problem that the invention seeks to solve]

The present invention provides that, in conventional methods, it is virtually impossible to remove high-boiling organic compounds such as unreacted monomers to a desired level from a polymerization system using a heavy substance having a boiling point of 100°C or higher. This was done to solve the problem that it is possible.

(Means for Solving the Problems) The present invention provides a method for producing a slurry of a polymer containing a high-boiling organic compound such as a residual monomer having a boiling point of 100"C or more.
High boiling point organic compounds can be removed from a slurry of a floating polymer without adversely affecting the quality of the polymer by contacting it with a carrier gas under strong stirring at high temperature in a processing device equipped with an agitator. This method is based on the discovery that high-boiling organic compounds are removed from a slurry of a buoyant polymer by contacting it with a non-condensable gas at high temperature and with strong stirring using a stirrer. .

〔Example〕

The vine polymer to which the present invention is applied is a polymer that has floating properties. Having floatability means that it will rise to the surface of the liquid if left undisturbed, and since a polymer with this property is used, strong stirring is essential to remove high-boiling point organic compounds such as unreacted polymers. This makes it possible to achieve sufficient dispersion of the polymer, and the method of the present invention makes it possible to remove high-boiling organic compounds present together with the polymer.

Specific examples of polymers with floating properties to which the present invention can be applied include, but are not limited to, ABS resins, HBS resins, As resins, etc. Any polymer can be applied as long as the polymerization system exhibits a slurry state and it is necessary to remove high-boiling point organic compounds from the polymerization system.

In the present invention, a slurry of a polymer having floating properties is used. Using a slurry can be stirred, high-boiling organic compounds can be effectively removed by contact with non-condensable gases, and there are fewer problems with foaming and scaling that occur with latex, making it economical. This is because it is preferable that the concentration is high.

Although the polymer concentration in the polymer slurry treated by the method of the present invention has a complex effect on the resistance to monomer transfer between gas and liquid, it is operated at 8 to 20% from the viewpoint of productivity and economy. is preferable. When the concentration is less than 8%, the productivity becomes very poor, and when it exceeds 20%, the resistance to movement of the monomer between gas and liquid becomes extremely large, and the removal efficiency tends to be poor.

When a slurry of a buoyant polymer is treated by the method of the present invention, the state of the polymer slurry may be a latex state, a solidified slurry state obtained by contacting the latex with an acid or a salt, or a solidified slurry state that is obtained by contacting the latex with an acid or a salt. There are three states: a heat-treated slurry state in which the slurry is heat-treated and hardened. Therefore, it is important to select in what state the polymer slurry should be treated with the present hair growth method in order to minimize quality deterioration and to more effectively remove high-boiling organic compounds such as residual monomers. is important.

As mentioned above, in the latex state, there are problems with foaming and scaling due to the injection of non-condensable gas as a carrier gas, and, for example, the above-mentioned HBS'&41
No. 11 requires a long treatment time to reduce the residual styrene monomer concentration to 101) or less, which is undesirable because it tends to lead to quality deterioration.

Since the mechanical strength of the polymer is weak in the solidified slurry state,
Although there are concerns about adverse effects such as breakage of coagulated particles during processing that involves strong stirring or during transfer of the coagulated slurry, the method of the present invention allows heat treatment during processing, so there is an advantage that heat treatment equipment can be omitted.

On the other hand, if a heat-treated slurry is treated by the method of the present invention, the disadvantages of solidified slurry having low mechanical strength will be eliminated, and the adverse effects on polymer quality will be minimized.

Therefore, it is preferable to apply the method of the present invention to polymers that are present as a coagulated slurry or a heat-treated slurry.

When treating solidified slurry or heat-treated slurry of a buoyant polymer by the method of the present invention, simply blowing carrier gas will cause the polymer particles to float, making it impossible to expect sufficient contact with the carrier gas. Therefore, the removal efficiency of residual monomers becomes very poor. The floatability increases rapidly with increasing treatment temperature, which is also very disadvantageous in the case of steam stripping. Therefore, it is preferable to uniformly disperse the polymer in the slurry by, for example, selecting an appropriate device.

The apparatus used in the method of the present invention is generally a stirred tank type or a bubble column type gas-liquid contact apparatus.

A simple bubble column type without a stirring basin requires the injection of a larger amount of carrier gas than necessary in order to compensate for the above-mentioned problem of buoyancy of the polymer, so it is inevitably economically disadvantageous.

On the other hand, the above-mentioned floating problem can be solved by stirring with a stirrer. In addition, in order to solve the floating problem, increasing the stirring number is effective in improving the dispersion of the carrier gas in the slurry, which is important in implementing the present invention, and is also a big economic disadvantage. does not occur. Naturally, when stirring is performed using a stirrer, the amount of carrier gas blown in can be reduced.

For the above reasons, when a polymer having floating properties, such as ABS resin or HBS resin, is used in the method of the present invention, the apparatus must be equipped with a stirrer.

As the non-condensable gas that is the carrier gas used in the present invention, any gas that exhibits a gaseous state at around room temperature can be used, such as nitrogen gas, helium gas, air, or a mixture thereof. Among these, gases that are inert to polymers, such as nitrogen gas, carbon gas, helium gas, argon gas, neon gas, etc., do not cause deterioration of the polymer and have safety concerns such as explosion and fire. Preferable from this point of view. Also, from an economic point of view, it is advantageous to use air.

For example, when removing residual styrene monomer from HBS@fat, the amount of carrier gas supplied is determined at a processing temperature of 7.
5-85°C, stirring Reynolds number 10s or more, preferably in the range of 105-10B, polymer concentration in slurry 8-2
1000% remaining in batch processing within 2 hours to avoid adverse effects on quality under 0% conditions.
In order to remove approximately Dl)l of unreacted monomer to a level of 10 ppm or less, the amount of carrier gas supplied per minute per treatment liquid (Nm3/win) (
When using the amount of dry air as (hereinafter referred to as VVH), 1 to 4 VVH is required.

Slurry of polymers with floating properties, such as HBS @
When high-boiling organic compounds such as residual monomers are removed from a fat slurry by the method of the present invention, the transfer resistance between gas and liquid of the high-boiling organic compounds from the slurry liquid to the carrier gas is is large, and this controls the movement of high-boiling organic compounds. Therefore, as mentioned above, in order to improve the efficiency of the method of the present invention, it is necessary to reduce the transfer resistance of the residual monomer between the gas and liquid by sufficient stirring, and to finely disperse the carrier gas in the slurry to increase the gas-liquid interface area. It is important to increase the

The high-boiling organic compound referred to in this specification refers to unreacted monomers having a boiling point of 100°C or higher, as well as impurities such as substances added during polymerization, decomposition products generated during polymerization, and side reaction products. Refers to substances with a boiling point of 100°C or higher that remain in the polymerization system.

The stirrer used in the present invention is used to stir the slurry of a polymer having floating properties at about 60 to 90°C. Preferably 75-85
It can be stirred at a high temperature of °C under strong stirring, preferably under conditions such that the stirring Reynolds number is 105 or more, more preferably 105 to 10, and at that time it can be brought into contact with a non-condensable gas. Specifically, there is no particular limitation as long as a non-condensable gas can be blown into the slurry to bring it into contact with the slurry and high-boiling organic compounds can be removed.

As shown in FIG. 1, the stirrer used in the present invention requires at least one stirrer for sufficient mixing of the polymer slurry in the apparatus and for sufficient dispersion of the supplied carrier gas.
A turbine mas+ of stages, preferably 1 to 4 stages, and the upper part thereof functions to prevent the floating of the polymer in the polymer slurry and to obtain sufficient removal efficiency of high boiling point organic compounds such as unreacted monomers. It is preferable to install at least one stage, preferably from 1 to 4 stages of paddle vanes, and furthermore, the uppermost paddle vane is arranged above the liquid level of the slurry when no gas is supplied from the non-condensable gas supply source (6). It is preferable that the polymer be present below the liquid surface when the non-condensable gas is supplied, in order to prevent the polymer from floating and to prevent the polymer from stagnation on the surface of the processing liquid. The position of the upper end of the paddle blade above the color of the baffle plate provided in the stirring tank (1) prevents the floating of the polymer and prevents the polymer from stagnation on the processing liquid surface, especially near the baffle plate. This is preferable from the viewpoint of prevention.

Next, the features of the method of the present invention for solving the problem of floating of the polymer in the slurry and improving the efficiency of contact between the carrier gas and the slurry will be described.

First, regarding the stirring blade, in order to finely disperse the carrier gas, it is effective to install a turbine blade such as a flat blade turbine, a pitted turbine, or a turbine with a disk near the carrier gas inlet. Among these, flat-blade turbine blades are preferred from the economic point of view, such as the power required for stirring.

Furthermore, depending on the amount of slurry to be processed and the liquid depth, several stages of turbine blades may be installed above the slurry in order to prevent a decrease in efficiency due to carrier gas coalescence and to achieve redispersion. Furthermore, near the liquid surface of the slurry to be processed, in order to prevent the polymer slurry from floating under the liquid surface, it is placed above the processing liquid surface when a carrier gas is not supplied, and is below the liquid surface when a carrier gas is supplied. It is preferable to install at least one stage of paddle blades at a suitable position.

The ratio of the diameter of the stirring blade to the diameter of the stirring tank should be set to 0 to prevent floating, to sufficiently disperse the carrier gas, and from an economical point of view.
．． The range of 3 to 0.5 is preferable.

From the viewpoint of preventing floating and obtaining a sufficient gas-liquid dispersion state, it is preferable that the stirring Reynolds number is 105 or more.

Next, regarding the baffle plates, approximately 3 to 4 baffles are installed for the purpose of improving the dispersion of the polymer slurry, and in order to prevent the polymer from stagnation near the baffle plates, the width of the baffle plates should be adjusted to the upper limit of the paddle size mentioned above. It is desirable that the height be lower than the position of , and that it is submerged in the processing liquid during the processing operation, that is, when the carrier gas is supplied.

If the baffle plate is exposed above the liquid surface during the treatment operation, the polymer will accumulate in the exposed portion, which is undesirable.

The higher the operating temperature in the method of the present invention, the greater the effect, but considering the negative effect on polymer quality,
It is desirable to keep the temperature below ℃.

Furthermore, even if the operation is carried out at 2i degrees below 85°C, the residence time, that is, the time during which the slurry is exposed to high temperatures below 85°C, should be kept within 2 hours, preferably within 1 hour. It is preferable that the process of the invention be carried out in batch operations within 2 hours, preferably within 1 hour; however, if the polymer is to be treated at temperatures below 85°C, continuous operations, semi-operations, etc. Batch operations are also possible, and there are no particular restrictions on the distribution method.The processing temperature is at least 75℃ due to the relationship between processing time and productivity.
It is preferable to maintain the temperature above.

In the method of the present invention, it is preferable to heat the polymer slurry to a predetermined operating temperature at the start of each batch operation, and during the operation, heat is removed by the exhaust gas of the carrier gas supplied. , it is preferable to constantly supply heat in order to keep the operating temperature constant. As a heat supply method, a general jacket method is sufficient, but in the present invention, the inside of the processing paddle is sufficiently agitated, so from the viewpoint of equipment cost, reduction of temperature rise time, etc., and productivity. It is more advantageous to raise the temperature by directly blowing steam or to control the operating temperature.

By treating a polymer slurry with floating properties by the method of the present invention, various processing properties of the polymer can be improved.
Efficiently removes residual unreacted monomers and high-boiling point organic compounds to a residual monomer level of 10 ppm (relative to a
It is possible to remove up to ll+1> or less.

Therefore, the method of the present invention is effective in improving odor, especially when these polymers are used as food packaging materials, and is also effective in improving health problems caused by high-boiling organic compounds such as unreacted monomers. This will greatly help eliminate the problem.

Next, the method of the present invention will be explained based on FIG. 1 for explaining one embodiment thereof, but the present invention is not limited thereto.

For example, the heat-treated slurry is supplied to the stirring tank (1), which is a stripping treatment device, from the slurry supply line (2J) until the liquid level of the heat-treated slurry is near the bottom of the paddle blade 4. paddle blade G coupled to fi stirrer drive device (9)
While continuing stirring to maintain the stirring Reynolds number at 101 or more using a stirrer having 41 and turbine blades (9), steam is supplied from the steam supply line (3), and the heat-treated slurry is subjected to a stripping treatment once. For example, the temperature is raised to 75 to 85°C.For example, a non-condensable gas which is a carrier gas of 1 to 4 VV14 in terms of dry air is supplied from a non-condensable gas supply source (6) such as a compressor, and steam is generated in the stirring tank. (1) Batch processing is usually carried out within 2 hours while maintaining the desired stripping temperature.

High boiling point organic compounds such as unreacted monomers are removed by carrier gas (
It is discharged from the exhaust gas line (71) to the outside of the yarn along with the air). After the stripping process, the steam supply is stopped,
The flow rate of the carrier gas is reduced, and the stripped heat-treated slurry is discharged to the outside of the stirring tank (1) by the pump (8).

By treating a polymer slurry having floating properties according to the method of the present invention, high-boiling organic compounds such as unreacted monomers occluded in the polymer in the slurry can be easily removed.

Next, the method of the present invention will be explained based on examples.

Example 1 and Comparative Example 1 A paddle blade and a flat turbine blade, each consisting of a device as shown in Fig. 1, have a blade diameter of 380 mm and a blade width of 80 mm.
A stripping device with a stirrer (diameter 900 mm, height 2000 mm) was charged with 500 mm of HBS polymer heat-treated slurry with a polymer particle concentration of 16% and an unreacted residual styrene concentration of 1200 ppm (relative to the resin), and steam was blown into the stripping device. After raising the temperature to 80℃, air was heated to (1.5N m”/Win
, 3VV14) Suki! Stripping was carried out for 60 minutes using 10g of fil Reynolds number 1.3x.

The residual styrene concentration of the polymer in the heat-treated slurry after the stripping treatment was Bpp-.

As a result of the sensory test, the odor was significantly improved compared to the sample without stripping treatment.

The granule properties and processing properties of the polymer were measured by the following methods. The results are shown in Table 1.

For comparison, granule characteristics and processing properties were also measured for samples that were not subjected to stripping treatment. The results are also shown in Table 1.

(Particle size distribution) Calculated by wet classification using a Tyler standard sieve, drying the powder on each sieve for 25 minutes using an infrared moisture content meter, and then measuring each weight.

(bulk specific gravity) Measured according to JIS 6721.

(Caking property) Fill a cylindrical container with an inner diameter of red with 30g of powder, and make a 25kl
) was compressed and solidified at air temperature for 2 minutes, and then subjected to T1121 for 200 seconds on a sieve vibrating at a frequency of 60H2S and an amplitude of 1■, and the disintegration rate (%) of the powder was measured.

()〇-Characteristics) Impacts of a certain intensity are applied to powder filled up to the upper edge of a hopper with hole diameter So, height 60mm, angle of 45°, and the number of impacts applied until all the powder in the hopper flows out. Measure.

(Angle of repose) Measured using a powder tester manufactured by Fine Micron ■.

(Izot strength) Measured by JIS 7110 method.

(transparency) Measured by the method of ASTH01003-61.

From the results in Table 1, it can be seen that the powder properties and processing properties of the polymer after the stripping treatment are the same as those without the stripping treatment.

〔Effect of the invention〕

By using the method of the present invention, high-boiling organic compounds can be effectively removed from a slurry of a polymer having floatability without impairing powder characteristics or processing properties.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the method of the present invention. (Main symbols in the drawing) (1): Stirring tank (z Nislary supply line (4): Paddle blade (S: Turbine blade (6): Non-condensable gas supply source (9): Stirrer drive device υ: Obstruction board

Claims (1)

[Claims] 1. A method for removing high-boiling point organic compounds from a slurry of a buoyant polymer by contacting it with a non-condensable gas at high temperature and with strong stirring using a stirrer. 2. The method according to claim 1, wherein the high-boiling organic compound is an unreacted monomer having a boiling point of 100°C or higher. 3. The method according to claim 1, wherein the agitator has at least one stage of turbine blades and at least one stage of paddle blades above the turbine blades. 4. The method according to claim 3, wherein the paddle blades are located above the liquid level of the slurry when non-condensable gas is not supplied, and below the liquid level when non-condensable gas is supplied. 5. The method according to claim 3 or 4, wherein the upper end of the paddle blade is located above the baffle plate. 6. The method according to claim 1, wherein the stirring operation is performed under conditions such that the stirring Reynolds number is 10^5 or more. 7. The method according to claim 1, wherein the concentration of the polymer in the slurry is 8 to 20% by weight.