JPH0759609B2 - Method for purifying high-molecular polymers - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for purifying a high-molecular polymer for purifying a crude high-molecular polymer in which various salts and the like are mixed in the high-molecular polymer.

(Prior Art) Conventionally, there is a method of using an ion exchange resin to remove various salts in a purification process of a high molecular polymer for purifying a crude high molecular polymer.

(Problems to be Solved by the Invention) By the way, in a method for purifying a high molecular polymer using an ion exchange resin, an object other than the high molecular polymer is adsorbed and removed by the ion exchange resin. However, there is a considerable loss of high molecular weight polymer because it is also absorbed. Further, in such a purification method, it is necessary to wash and regenerate the ion exchange resin at an early stage, and it takes time and labor to purify the polymer.

Accordingly, it is an object of the present invention to address the above problems using ceramic filters for the purification of high molecular weight polymers.

(Means for Solving the Problems) The present invention is a method for purifying a crude high-molecular polymer in which various salts and the like are mixed in the high-molecular polymer, and the polymerizing reaction is performed in the crude high-molecular polymer. The solvent used in step 1 is added to form a diluted liquid to be treated, and the liquid to be treated is supplied to a filter containing a ceramic filter and circulated while flowing along one side of the filter, During this period, a part of the liquid to be treated is made to permeate to the other side of the filter by a pressure difference and flow out.

(Operation and Effect of the Invention) In such a purification method, in the liquid to be treated formed by adding the solvent to the crude high molecular weight polymer, the mixed substances such as salts other than the high molecular weight polymer are in a dissolved state and the high molecular weight polymer is high. The polymer is in a dispersed state, and when the liquid to be treated is circulated while flowing along one side of the ceramic filter,
A part of the liquid to be treated permeates to the other side of the filter due to the differential pressure and flows out. In the filtrate that has flowed out, the above-mentioned mixed substances are dissolved, and the purity of the high-molecular polymer in the remaining liquid to be treated is increased, and the same dilution is caused by the solvent of the liquid to be treated and the sieving action of the ceramic filter. The mixed substance in the liquid to be treated is none or close to this, and a purified high molecular polymer is obtained. In such a purification process, a part of the high molecular weight polymer in the liquid to be treated is attached and deposited on one side of the filter, but since the liquid to be treated is constantly flowing along one side of the filter, the polymer deposition thickness Is kept almost constant by the shearing force of the liquid to be treated, and the permeation of the liquid to be treated is stable and continues for a long time. Therefore, according to the purification method of the present invention, a high-purity high-molecular polymer can be efficiently purified.

EXAMPLES The present invention will be described below with reference to the drawings. FIG. 1 shows a purifying apparatus for carrying out the purifying method of the present invention, and FIG. 2 shows experimental results of the purifying method. An example is shown.

(1) Refining apparatus The refining apparatus shown in FIG. 1 is for carrying out an example of the refining method of the present invention, and is equipped with a circulation tank 11, a circulation pump 12 and a filter 13, which are in a circulation line. Are connected in series. Supply line 14 that constitutes such a circulation line
A circulation pump 12 is provided between the circulation tank 11 and the filter 13 of a, and a drain line is provided between the pump 12 and the circulation tank 11.
15a is connected, and the tip of the supply conduit 14a is connected to the filter 13 and communicates with the inner peripheral side of the cylindrical ceramic filter 13a housed in the filter 13. The base end of the reflux conduit 14b that constitutes the circulation conduit communicates with the inner peripheral side of the filter 13a, similar to the supply conduit 14a connected to the filter 13, and the outflow pipe connected to the filter 13a. The path 15b communicates with the outer peripheral side of the filter 13a. In the purification apparatus, a circulation tank 11 is connected to a cooling tank 22 connected to a polymerization vessel 21 of a suspension polymerization apparatus for vinyl acetate polymer, and the circulation tank 11 contains a suspension cooled after a polymerization reaction. Supplied.
Further, pure water is supplied into the circulation tank 11 through the water supply pipe line 15c, and the suspension contained in the circulation tank 11 is diluted to prepare a liquid to be treated.

Then, the liquid to be treated prepared in the circulation tank 11 in the refining device is circulated by the drive of the circulation pump 12 and supplied to the filter 13, and the liquid to be treated in the filter 13 has an inner circumference of the filter 13a. Flow along the side and during this filter 1
A part of the liquid to be treated permeates due to the pressure difference between the inner and outer peripheral sides of 3a and flows out as a filtrate from the outflow conduit 15b. As a result, the vinyl acetate polymer in the liquid to be treated remains in the liquid to be treated, and other contaminants in the liquid to be treated are removed while being dissolved in the filtrate. Incidentally, the treatment liquid remaining in the circulation tank 11 after the purification treatment of the liquid to be treated flows out of the system through the drain conduit 15a, and similarly the cake deposited on the inner peripheral surface of the filter 13a is a filter 13a using pure water. It is peeled off by backwashing and washed out with pure water. Water is removed from these effluents by a centrifuge and further dried by a drier to obtain a highly pure vinyl acetate polymer.

(2) Purification Experiment In the polymerization process of vinyl acetate polymer using the purification apparatus shown in FIG. 1, a purification experiment of the polymer was conducted under the following conditions.

-Undiluted solution: Liquid containing vinyl acetate polymer and various salts cooled after completion of suspension polymerization, SS concentration 100 g /, specific gravity 1.0
2 (25 ℃), viscosity 1.3cp (40 ℃), PH3.5 (25 ℃), electric conductivity 527μS / cm (25 ℃) ・ Additional solvent: pure water. Electric conductivity 1μS / cm ・ Filter: Cylindrical ceramic filter, outer diameter 10mm, inner diameter 7mm, length 500mm 1 piece, filtration area 0.011m ² , average pore size 0.
2 μm ・ Filtration: Pure water 10 is added to the undiluted solution 10 to prepare 20 undiluted solutions, which are circulated and supplied to the filter, and the supply is stopped when the outflow of the filtrate reaches 10. (1 filtration times). Then, pure water 10 was added to the remaining liquid to be treated 10 to prepare 20 more liquids to be treated, and the same filtration treatment (the number of filtration times 2) as described above was performed, and the filtration treatment was repeated.

-Evaluation method: The electric conductivity of the residual liquid after each filtration treatment was measured, and the degree of removal of the contaminants in the vinyl acetate polymer suspension was estimated based on the decrease in the electric conductivity.

The graph of FIG. 2 shows the result of the purification experiment conducted under such conditions. As shown in this graph, the electric conductivity is 52
The stock solution to be treated, which had been 7 μS / cm, had an electric conductivity of 82 μS / cm with one filtration, an electric conductivity of 9 μS / cm with two filtrations, and an electric conductivity of 1.5 μS / cm with three filtrations, which was almost pure water. It was found that a high-purity vinyl acetate polymer suspension can be obtained by repeating the filtration treatment three times.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a purification apparatus suitable for carrying out the purification method of the present invention, and FIG. 2 is a graph showing the result of an example of the purification method. Explanation of symbols 11 …… Circulation tank, 12 …… Circulation pump, 13 …… Filter, 13a …… Filter.

Claims (1)

[Claims] 1. A method for purifying a crude polymer, in which various salts and the like are mixed in the polymer, wherein a solvent used in the polymerization reaction is added to the crude polymer. To form a diluted liquid to be treated, supply the liquid to be treated to a filter containing a ceramic filter, and circulate while flowing along one side of the filter,
During this period, a part of the liquid to be treated is permeated to the other side of the filter by a pressure difference to flow out, and a method for purifying a high molecular polymer.