JP2003292527A - Method for coagulating polymer latex - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coagulation method enabling efficient and stable production of a polymer. <P>SOLUTION: Steam is directly blown into a liquid containing a polymer latex obtained by emulsion polymerization in a container in which the coagulation is carried out by inserting a pipe for feeding the seam in the liquid when coagulating the polymer latex by bringing the latex into contact with a coagulating agent. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polymer latex obtained by an emulsion polymerization method. More specifically, the present invention relates to a method for coagulating a polymer latex obtained by an emulsion polymerization method.

[0002]

BACKGROUND OF THE INVENTION In emulsion polymerization, water is used as a medium for controlling the reaction temperature, and an insoluble or sparingly soluble monomer and an emulsifier are added to the aqueous medium to disperse them as micelles in water. It is a polymerization mode in which it is dissolved to initiate polymerization, and is widely used industrially. In this emulsion polymerization, since the polymerization proceeds in micelles of the monomer, it is easy to control the polymerization temperature, the polymerization rate is fast, and usually a polymer having a large molecular weight is easily obtained.

On the other hand, since the product after the reaction is in a polymer latex (that is, emulsion) state, it is necessary to separate the polymer from the polymer latex depending on the use of the obtained polymer. Conventionally, various methods have been developed to separate the polymer from the polymer latex in this way.

As a method for recovering a polymer latex produced by emulsion polymerization as a solid or powder, generally, the latex is brought into contact with a coagulant such as an acid or a salt to coagulate it and then dehydrated. There is a wet coagulation method of drying and collecting as a powder.

[0005]

However, in this wet coagulation method, when indirect temperature control such as a jacket is used to control the temperature of the container (coagulation tank) in which latex is coagulated, the jacket- Since heat conduction between the coagulation tanks is generally not good, there is a problem that it takes time to control the temperature of the coagulation tanks.

Therefore, there is a strong demand for a method for coagulating a polymer which is efficient and has stable productivity.

An object of the present invention is to provide a method for coagulating a polymer, which solves the above-mentioned drawbacks of the prior art.

Another object of the present invention is to provide a coagulation method which enables efficient and stable production of a polymer.

[0009]

As a result of earnest research, the inventor of the present invention did not adjust the temperature indirectly as in the prior art, but rather immerses the pipe in the liquid and blows the vapor directly into the liquid. Have been found to be extremely effective in achieving the above-mentioned object.

The method for coagulating a polymer latex of the present invention is based on the above findings, and more specifically, the method for coagulating a polymer latex obtained by contacting a polymer latex obtained by an emulsion polymerization method with a coagulant. In a container to be subjected to the coagulation, by immersing a steam supply pipe in a liquid containing the polymer latex and directly blowing steam into the liquid to control the temperature in the container. It is a feature.

The temperature control according to the present invention having the above-described structure has an advantage that the liquid to be temperature-controlled is directly heated and the temperature change response speed is excellent. In addition, the method of the present invention can easily be made extremely excellent in thermal efficiency, and can realize a preferable form as a production apparatus.

In the coagulation method of the present invention having the above structure, a gas may be blown into the liquid containing the polymer latex together with the steam or in place of the steam, if necessary. In such an embodiment in which gas is used in combination, for example, when a vapor supply line and a gas supply line are connected to a vapor supply pipe of a coagulation tank and vapor is not blown into the liquid, It is preferable to blow the gas at a linear velocity of 2 to 50 m / s.

Further, a control valve is provided in the steam supply line, and the opening of the control valve is 1.0 to
It is preferable to open the open valve at any value of 20.0% to start blowing gas. On the other hand, in the process of increasing the opening of the control valve,
It is preferable to close the open valve and stop the gas blowing at the time when the opening degree of the control valve is an arbitrary value of 1.0 to 20.0%.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically with reference to the drawings as necessary. In the following description, "part" and "%" representing the quantitative ratio are based on mass unless otherwise specified.

In the method for coagulating polymer latex of the present invention, the polymer latex is brought into contact with a coagulant to coagulate it to obtain a coagulated polymer (for example, polymer powder). In a container (for example, a coagulation tank) to be subjected to coagulation), a pipe for supplying steam is immersed in the liquid, and steam is directly blown into the container.

(Emulsion Polymerized Latex) In the present invention,
The latex to be coagulated is not particularly limited as long as it is a latex obtained by emulsion polymerization. More specifically, for example, a hard non-elastic polymer latex or an elastic polymer latex can be used.

(Coagulant) The coagulant usable for coagulating the emulsion-polymerized latex is not particularly limited. Usually, the coagulant to be used in this case depends on the emulsifier used in producing the emulsion polymer latex. That is, when the emulsifier used is a weak acid salt such as a carboxylic acid salt, an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid or an inorganic salt such as calcium chloride, magnesium sulfate or aluminum sulfate as a coagulant for the emulsion polymerization latex. An organic acid salt such as calcium acetate or aluminum acetate can be used. From the viewpoint of easy separation of the emulsifier, it is preferable to use an inorganic acid.

When a strong acid salt such as a sulfate ester salt is used as an emulsifier used in the production of the emulsion polymer latex, the emulsifier can be easily separated as a coagulant for the emulsion polymerization latex. From the standpoint of use, it is preferable to use inorganic salts such as calcium chloride, magnesium sulfate and aluminum sulfate; organic acid salts such as calcium acetate and aluminum acetate.

The coagulant is preferably used in an amount sufficient to coagulate the emulsion polymer latex. The amount of the coagulant may vary depending on the type of the coagulant and the type and content of the emulsifier in the emulsion polymer latex,
Generally, it is preferably 0.5% by weight or more, and more preferably 1.0% by weight or more based on the solidified polymer. If the amount of the coagulant used is less than 0.5% by weight, it tends to be difficult to sufficiently solidify the polymer particles, and the water content of the obtained solidified polymer increases. Productivity in the subsequent drying process tends to decrease.

(Steam) In the present invention, the type of steam, the mode of supply, etc. are not particularly limited as long as the temperature control is possible. From the viewpoint of the influence on the physical properties of the powder obtained by solidification, steam can be preferably used.

The steam may be supplied, for example, continuously or intermittently, may be supplied at a constant flow rate, or may be appropriately changed (eg, steam flow rate). May be gradually increased and / or decreased).

(Steam Supply Pipe) The type, thickness, length, material and the like of the steam supply pipe are not particularly limited as long as they can be used for temperature control in the present invention.

(Immersion) As long as it can be subjected to temperature control, the mode and degree of immersion of the steam supply pipe,
Etc. are not particularly limited.

(Gas) In the present invention, a gas can be blown into the liquid containing the polymer latex together with the steam or in place of the steam, if necessary. By additionally using gas blowing in this way, the risk of polymer powder generated by coagulation entering the vapor supply pipe and clogging the pipe can be further reduced.
In particular, when vapor is intermittently blown into the liquid, it is preferable to use the gas as described above.

In the present invention, the kind of gas to be supplied into the liquid through the gas supply line or the like is not particularly limited. As this gas, for example, air or nitrogen can be appropriately selected and used as necessary.

In the present invention, the gas is preferably blown at a linear velocity in the range of 2 to 50 m / s,
It is particularly preferably 10 to 25 m / s. When the amount of gas blown is less than 2 m / s, the coagulated and solidified polymer tends to easily enter the vapor supply pipe. On the other hand, when the amount of gas blown in is greater than the linear velocity of 50 m / s, the liquid level tends to rise violently and easily.

The gas to be supplied may be used by circulating it by installing a blower or the like on the upper part of the coagulation tank. Such a mode of reuse or circulation is preferable from the viewpoint of safety, because it is not necessary to release the coagulant contained in the gas to the outside of the tank.

(Solidifying Step) The solidifying step may be carried out in one stage operated at a constant temperature (that is, coagulation and solidification in one stage) or in two or more stages in which the temperature is raised stepwise. However, it is preferable to carry out in two or more steps from the viewpoint of more solidifying the solidification.

In the coagulation step, when the emulsion polymer latex is a rubber-like elastic polymer latex,
To improve the bulk density and blocking resistance of the coagulated polymer obtained after drying, a hard non-elastic latex may be added.

After carrying out the coagulation step and the solidification step in this way,
The obtained slurry can be centrifugally dehydrated and dried to obtain a coagulated polymer.

(One Embodiment of Apparatus System) A basic one embodiment of an apparatus system which can suitably carry out the solidification method of the present invention is shown in a schematic sectional view of FIG.

Referring to FIG. 1, a liquid 2 containing a polymer latex to be coagulated is placed in a coagulation tank 1 for coagulating the polymer latex. On the other hand, the temperature-adjusting steam supply pipe 3 is arranged so that the tip of the pipe 3 is immersed in the liquid 2. The pipe 3 is connected to a steam supply line 5 via a steam control valve 4.

(Coagulation Method) In the present invention, the specific method for coagulating the emulsion-polymerized latex is not particularly limited as long as the steam is directly blown into the liquid in the tank to control the temperature in the tank. For example, three-way swept blades, propeller blades, turbine blades,
Using a continuous stirring tank with three stirring tanks equipped with stirring blades such as paddle blades and disk blades, the first tank is used as a coagulation tank for coagulation, and the second and subsequent tanks are solidified for solidification. When used as a tank, the coagulation step and the solidification step can be continuously performed, which is preferable from the viewpoint of productivity and equipment cost. In such an embodiment in which the coagulation tank and the solidification tank are separated from each other, the emulsion polymer latex and the coagulant solution are added to the coagulation tank, and these are contacted in a stirring tank to coagulate. It can be performed.

As a method of adding the emulsion polymer latex and the coagulant solution to the coagulation tank, for example, only the coagulant solution is previously fed into the coagulation tank, and then the emulsion polymer latex is added thereto. And a method of continuously adding the coagulant solution and the emulsion polymer latex to the coagulation tank at the same time. The addition method includes a method of immersing the nozzle in a coagulation tank, setting it, and discharging continuously from this nozzle, a method of dropping from above the tank, and the like. In the present invention, the temperature control in the coagulation step and the solidification step (a mode in which the coagulation tank and the solidification tank are separated) is performed by, for example, blowing from a vapor supply pipe installed by being immersed in the liquid of each tank. It can be carried out by steam. If necessary, temperature detecting means for detecting the temperature inside the tank can be arranged in each tank.

In such temperature detection, for example,
A temperature sensor may be installed in each tank, and the temperature inside the tank read by the temperature sensor may be read by a computer connected to the temperature sensor. The preset temperature is input to the computer in advance, and the computer adjusts the temperature inside the tank by adjusting the opening of the control valve installed in the steam pipe to adjust the amount of steam blown into each tank. can do.

(Other Embodiments of Apparatus System) Another basic embodiment of the apparatus system which can preferably carry out the solidification method of the present invention is shown in the schematic sectional view of FIG. In the embodiment of FIG. 2, a gas supply line 7 is connected to the steam supply pipe 3 for temperature control of FIG. 1 through an open valve 6 for gas flow rate control.
1 is the same as that of FIG. 1 except that is connected.

(Aspect in which Gas is Used in Combination) In the aspect shown in FIG. 2, the vapor supply line 3 is connected to the vapor supply pipe 3.
And the gas supply line 7 are connected. For example, the gas supplied from the gas supply line 7 is constantly blown into the liquid 2 while the steam is not blown from the steam supply line 5.

According to the structure shown in FIG. 2, the powder produced by the coagulation of the polymer latex is contained in the steam supply pipe.
It is possible to more effectively prevent problems such as invasion into the pipe and blocking the pipe.

The gas from the gas supply line 7 is
The opening of the control valve 4 of the steam supply line 5 (op
The opening is 1.0% to
At any predetermined value between 20.0%, the open valve 6 installed in the gas supply line 7 is opened,
It is preferable to start blowing gas from the gas supply line 7.

On the contrary, in the process of increasing the opening degree of the control valve, when the opening degree reaches an arbitrary predetermined value between 1.0% and 20.0%, it is installed in the gas supply line 7. It is preferable that the opened valve 6 is closed so that the blowing from the gas supply line 7 is stopped. The opening of the control valve at which the gas injection is started or stopped is not particularly limited as long as it is in the range of 1.0 to 20.0%, but is preferably 5.0 to 10%. . Even if the blowing of gas is started or stopped when the opening of the control valve is smaller than 1.0%, the powder that has already coagulated may have entered the steam supply pipe, which is not preferable. . On the other hand, the opening is 20.0
When the gas blowing is started or stopped at a time point higher than%, the tendency that the liquid level in the tank rises up increases.

(Other Embodiments of Apparatus System) Another basic embodiment of the apparatus system which can preferably carry out the solidification method of the present invention is shown in the schematic sectional view of FIG. In the embodiment of FIG. 3, a blower 8 is installed above the coagulation tank 1 of FIG.
It is possible to circulate the gas blown into the coagulation tank 1 for use. By using the gas in a circulating manner in this manner, an additional advantage of safety can be obtained.

[0042]

EXAMPLES In the examples, "parts" and "%" represent "parts by weight (parts by weight)" and "% by weight (% by weight)", respectively.

Example 1 [Preparation of emulsion polymer latex]

1 part of dipotassium alkenyl succinate, 0.02 part of n-octyl mercaptan and 80 parts of methyl methacrylate were placed in a reaction vessel equipped with a stirrer (material: Pyrex (registered trademark) glass, internal volume 5.0 liter).
20 parts of butyl acrylate and 260 parts of water were charged, 0.15 part of potassium persulfate was added, and polymerization was carried out at 60 ° C. for 2 hours.

Further, 0.1 part of t-butyl hydroperoxide and 0.12 part of formaldehyde sodium sulfoxylate were added and polymerization was carried out at 62 ° C. for 2 hours to obtain an emulsion polymer latex (Tg = 57 ° C. Refractive index: 1 .48
5) was obtained.

[Coagulation Process] Three coagulation processes were carried out by connecting two 5.0 L overflow agitation tanks (solidification tanks) in series downstream of a 3.6 L overflow agitation tank (coagulation tank). .
A three-way swept blade was used as the stirring blade.

An immersion nozzle for supplying the emulsion polymer latex was provided in this coagulation tank at a position of 45 degrees in the clockwise direction (the same direction as the stirring rotation direction) from the overflow port as a starting point from the upper surface of the tank. This immersion nozzle is immersed vertically to the liquid surface,
It was set so that the depth of the discharge port was 50 mm from the liquid surface. At this time, the direction of the discharge port was set so that the discharge direction was the direction of the main flow in the stirring tank.

Next, the coagulant aqueous solution supply position was set at a position separated by 50 mm from the wall surface at an angle of 180 degrees clockwise starting from the overflow port.

The steam supply pipe is provided at a position of 45 degrees counterclockwise (opposite to the stirring rotation direction) from the upper surface of the tank with the overflow port as a starting point, and the pipe is immersed vertically to the liquid surface and blown into the injection port. It was installed so that the depth of was 30 mm from the bottom of the tank.

Further, a thermocouple for monitoring the temperature in the tank is provided at a position of 120 degrees counterclockwise (a direction opposite to the stirring rotation direction) starting from the overflow port, and the depth of the tip of the thermocouple is 70 mm from the liquid surface. Was installed.

Air is used as the blowing gas, and it is set so that the blowing of air is started when the opening of the control valve of the steam supply line reaches 5.0%, and the blowing speed is 18 m / s. did.

A 0.48% sulfuric acid aqueous solution was used as a coagulant, and the temperature of each tank was set to coagulation tank / solidification tank 1 / solidification tank 2 = 60 ° C.
/ 60 ° C / 95 ° C, the coagulation tank, the solidification 1 tank, and the stirring speeds of the 2 tanks are 365 rpm, 365 rpm, and 3 rpm, respectively.
It was set to 24 rpm.

Then, the emulsion polymer latex was discharged from the dipping nozzle at 6.6 kg / hr, and the 0.48% sulfuric acid aqueous solution was added at 7.26 kg / hr [latex / sulfuric acid = 1 / 1.1].
(Polymer solid content concentration in coagulation tank: 22.2%)], and the continuous addition was performed in the coagulation tank for continuous coagulation.

After the steady state was reached, the coagulation liquid slurry was sampled from the outlet of the final tank.

The amount of coagulant under this coagulation condition was 100
1.1 parts to 1 part, and the measured pH in the coagulation tank is 1.
It was 6.

[Recovery of Polymer Particles]

The obtained coagulated liquid slurry was dehydrated by a centrifugal dehydrator (Tanabe upper discharge type O-20 type) (1800 rp).
m: 3 minutes), and then dried using a batch type fluidized dryer set to a hot air temperature of 80 ° C. to obtain polymer particles.

In the solidification method according to this example, polymer particles did not adhere to the pipe, and continuous operation was possible without problems.

[0059]

As described above, according to the present invention, it is possible to efficiently and stably produce a polymer.

Furthermore, in the embodiment of the present invention in which a gas is used in combination, for example, by continuously blowing the gas into the steam supply pipe when the steam is stopped, it is possible to efficiently and more stably produce polymer particles. .

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of an apparatus system capable of suitably carrying out the solidification method of the present invention.

FIG. 2 is a schematic cross-sectional view showing another aspect of an apparatus system capable of suitably carrying out the solidification method of the present invention.

FIG. 3 is a schematic cross-sectional view showing another aspect of an apparatus system capable of suitably carrying out the solidification method of the present invention.

[Explanation of symbols]

1 ... coagulation tank 2 ... Liquid containing latex 3… Steam supply piping 4 ... Control valve 5 ... Steam supply line 6 ... Open valve 7 ... Gas supply line 8 ... Blower

Claims (5)

[Claims] 1. A method for coagulating a polymer latex obtained by contacting a polymer latex obtained by emulsion polymerization with a coagulant; in a liquid containing the polymer latex in a container in which the coagulation is to be carried out. A method for coagulating a polymer latex, which comprises immersing a pipe for supplying steam in the above and blowing the steam directly into the liquid to control the temperature in the container. 2. The method for coagulating a polymer latex according to claim 1, wherein a gas is blown into a liquid containing the polymer latex together with or instead of the vapor. 3. When the vapor is not blown into the liquid or when the supply of the vapor tends to decrease, the gas containing the polymer latex is fed at a linear velocity of 2 to 50 m / s. The method for coagulating the polymer latex according to claim 2, wherein the polymer latex is blown. 4. A control valve is provided in the middle of the line to which steam is supplied, and the opening of the control valve is 1.0 to 20.
At an arbitrary value of 0%, the open valve for controlling the gas injection is opened to start the gas injection; in the process of increasing the opening of the control valve, the opening is 1.0 The method for coagulating a polymer latex according to claim 2 or 3, wherein the open valve is closed at an arbitrary value of 20.0% to stop gas blowing. 5. The method for coagulating a polymer latex according to claim 2, wherein the gas supplied into the container is circulated from the inside of the container and reused for blowing gas into the container. .