JPS60166324A - Apparatus for continuous washing of polyamide chip - Google Patents

Abstract

PURPOSE:To provide an apparatus capable of removing low-molecular compound extremely effectively and economically, by attaching a nozzle for the forced suction of extraction liquid and a nozzle for ejecting the monomer-containing extraction liquid to the middle part of the column in a one-column continuous washing of polyamide chips containing low-molecular compound. CONSTITUTION:The chips A are slid down from the introduction nozzle 2, and the extraction liquid B is supplied from the bottom nozzle 4 of the column. The chips and the liquid are brought into contact countercurrently with each other, and the extraction liquid is overflowed from the nozzle 5, while the chips are discharged continuously from the nozzle 3. The extraction liquid is sucked forcibly from the suction nozzle 10 furnished with a filter and attached to the middle part of the column 1 via the connecting pipes 15, 17 to the pump 18. In the course of the suction of the liquid, a definite amount of monomer is supplied from the connection pipes 19, 21 to the connection pipe 16 by the pump 20, and the liquid is recycled and sprayed in the column radially through the dispersion nozzle 9 (having spraying holes at the inner and outer circumferences). The suction nozzle 10 is placed nearly at the same level as the spraying holes of the dispersion nozzle 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an apparatus for removing low molecular weight compounds from polyamide chips containing monomers and oligomers (hereinafter referred to as low molecular weight compounds).

If a conventional polyamide chip contains a large amount of low-molecular-weight compounds, a number of problems such as thread breakage occur when the chip is melt-spun or melt-molded as it is.

Therefore, when the polyamide depth obtained in the polymerization process contains a large amount of low-molecular-weight compounds, for example, in the case of polyε-caprolactam depth (nylon-6), it is necessary to carry out post-processing before supplying it to the spinning or molding process. Low molecular weight 16
compound is removed.

Many methods and devices for obtaining polyamide chips with a low content of low-molecular-weight compounds have been proposed, but none of them have been satisfactory in terms of economy or performance. When cleaning is performed under industrial conditions using an extractant that does not contain monomers (for example, pure water) or an extractant with a low monomer concentration, the residual low-molecular-weight compounds in polyamide chips are only about i, owt%. Does not decrease. The reason for this is thought to be that 80 to 90% of the 1.0 wt % low molecular weight compounds remaining in the chip are oligomers, and oligomers are difficult to dissolve in water.

Even when washing with a hot water extractant, the removal of the A ribomer is not sufficient, and in a continuous washing device, the extract is extracted at a position of 30 to 60% from the start of washing of the column, and the monomer concentration at the top of the column is reduced to 5 to 10%. Method 6 (Japanese Unexamined Patent Publication No. 101898/1989) has been shown to improve the oligomer removal effect by removing the oligomer from the top of the column. At the same time, the concentration of oligomers contained in the extractant increases, and there is a fear that the ability to continuously and steadily remove oligomers from the chip may decrease. On the other hand, conventional methods for effectively removing oligomers include a multi-column continuous system using two or more towers or a batch system, but multi-column single-batch cleaning requires less running costs and equipment compared to single-column cleaning. The problem is that it is very expensive.

Technical Background of the Invention The present inventors first investigated the monomer concentration distribution and residence time of low-molecular-weight compounds in polyamide chips in a single-column continuous washing system for polyamide chips in a batch type or continuous two-column type. Regarding the content, we simulated and studied the optimal extraction liquid monomer m degree distribution in a single-column type washing tower. It has been said in the past that by increasing the concentration of 7-mer at the top of the column, oligomer components in the chips retained in the column top region can be effectively removed, and highly water-soluble monomer components can be reduced to 7-mer at the bottom of the column. Extract with low concentration (
This is a continuous cleaning method in which the extract liquid is removed using pure water at the inlet of the bath. Here, in the method described in JP-A-54-101898, which aims to improve the removal efficiency of oligomer components by increasing the monomer concentration at the top of the column by withdrawing the extract from the middle of the column, the extract at the top of the column is In order to increase the oligomer concentration in the tower in parallel, the present inventor installed a nozzle at an arbitrary position, especially an intermediate position, and injected the monomer from the nozzle in order to improve the heptamer concentration at the top area of the tower. We aimed to improve the removal efficiency of oligomer components. In this method, a certain amount of extract liquid is always injected and at the same time, a certain amount of extract liquid overflows and flows out of the tower, so the oligomer concentration at the top of the tower increases above a certain value even during continuous use. There is no problem and the oligomer removal effect can always be efficiently obtained.

Next, the inventors investigated a number of methods for uniformly injecting the 7-mer solution, which is about 1/1 of the amount of the extract, into a flow in which the difference in countercurrent relative velocity between the chip and the extract is less than a few minutes. I sang it. As a result, the upward flow rate of the extract is slow in the lactam-only injection method.

Due to the countercurrent flow of the chips and the small amount of liquid injected, it is difficult to completely homogenize and mix the mixture by blowing out. Therefore, the extract liquid is forcibly drawn out of the column from the middle of the column and the monomer is injected into the extracted liquid. However, they found that it is extremely effective to blow out the necessary homogeneous monomer component into the column together with the extract, leading to the present invention.

Structure of the Present Invention The present invention involves moving a polyamide depth containing monomers and oligomers downward from the top of the washing tower, and an extracting agent moving upward from the bottom, bringing the chips and the extractant into countercurrent contact with each other, thereby removing the polyamide chips from the polyamide chips. And, in a polyamide chip cleaning device that continuously extracts and removes oligomers, a cleaning liquid dispersion nozzle and a suction nozzle corresponding to the dispersion nozzle are arranged at an intermediate position of the cleaning tower at almost the same level, and the suction nozzle and the dispersion nozzle is connected to a pipe line having a circulation pump installed outside the tower to form a liquid circulation circuit, and
This continuous polyamide chip cleaning apparatus is characterized in that a supply nozzle for injecting monomer in a fixed amount is connected to the liquid circulation circuit.

The present invention will be explained below based on the drawings. FIG. 1 is a schematic explanatory diagram showing a specific example of the present invention. In the figure, reference numeral 1 denotes the main body of the cleaning tower, and the top and bottom of the tower have chip introduction nozzles 2 and 2, respectively. An outlet nozzle 3 is provided. In addition, an extraction liquid supply nozzle 4 is attached to the bottom of the column, and a discharge nozzle 5 is attached to the top of the column. It is designed so that it can overflow and come out from the nozzle 5.

Reference numeral 6 denotes a liquid circulation line, which includes an annular supply pipe 7 disposed horizontally and coaxially with the cylindrical column body 1 between the nozzles 4 and 5 in the middle of the column body 1, as shown in FIG. A dispersion nozzle 9 having a plurality of radially oriented dispersion holes 8 on the inner and outer peripheral surfaces of the tube 7. A suction nozzle 10 having a filter 11 located approximately at the same position as or slightly below the center of the annular supply pipe 7 (the supply pipe 7, the suction nozzle 10, etc. is 1/2 to 2/2 of the height of the tower body 1 from the bottom of the tower). 3), a nozzle 12.13 attached to the column body 1 and a supply pipe 7. Connecting pipe 14.15 connecting suction nozzle 10. Connecting pipe 16.1 connecting nozzle 12.13 and circulation pump 18 located outside the tower
It is made up of 7 connected. Furthermore, a monomer supply line 19 that communicates with a pump 20 that supplies a fixed amount of monomer is connected to the connecting pipe 16 of the liquid circulation line 6 via a nozzle 21, so that a predetermined amount of monomer is continuously supplied to the connecting pipe 16. It is made to be done. The monomer feed pressure to the connecting pipe 16 is maintained at a higher pressure side than the liquid circulation line pressure by a non-illustrated check valve or the like, and a heat-retaining trace is provided. Incidentally, the monomer supply line 19 may be connected to other continuous pipes 14, 15, 17, etc.
A mixer may be provided in the i'i pipes 14 to 17.

The installation position of the dispersion nozzle 9 is determined depending on the chip residence time, the required amount of residual low molecular weight compounds in the chips, etc., but it is usually installed at a height of 1/2 to 2/3 from the bottom of the column. Good. The structure of the dispersion nozzle 9 is preferably formed into an annular shape similar to the cross-sectional shape of the column main body so that the liquid is dispersed horizontally from the inner and outer peripheral surfaces thereof, but the structure is not limited thereto. Since the flow velocity distribution of the extract in the tower has a lower velocity on the wall side, it is preferable to have more dispersion holes 8 on the outer circumferential side than on the inner circumferential side.

Effects In the apparatus having such a configuration, the chips A are slid down by their own weight from the introduction nozzle 2 at the top of the column, and the extract B is supplied from the nozzle 4 at the bottom of the column, and the chips A and extract B are Due to the alternating current contact, the extract overflows from the nozzle 5, and the chips are continuously discharged from the nozzle 3, respectively.

In this case, the extract flowing into the liquid circulation line from the J5 C suction nozzle 10 passes through the communication pipe 15.17 to the -C circulation pump 18, and from there is further sent to the dispersion nozzle 9 via the communication pipe 16.14. However, since a fixed amount of monomer is continuously supplied to the communication pipe 16 by the pump 20, the extract containing a fixed amount of monomer is radially released from the dispersion holes 8 on the inner and outer peripheral surfaces of the dispersion nozzle 9. leak.

Here, the suction nozzle 10 is at almost the same level as the dispersion nozzle 9, especially the dispersion hole 8 (the level position relative to the dispersion hole is O~--
(preferably about 100m/m),
The extract having a high monomer concentration blowing out from the dispersion hole 8 is diffused very well, and the back 70 is directed toward the bottom of the column.
− is prevented. For this reason, the high mW monomer in the upper part of the dispersion nozzle 9 is in an extremely uniform state, and the removal of oligomer components in the whelks that come into countercurrent contact with the extract in this area (top area) is very effective. It is carried out according to The chips continue in the area below the next dispersion nozzle 9 (bottom area).
The main binding τ monomer component is removed by the extract liquid supplied from the bottom of the tower, and chips of good quality with low remaining low molecular weight compounds are stably obtained by being taken out from the nozzle 3 at the bottom of the tower.

The liquid circulation m in the liquid circulation line is preferably 5 to 15 times, especially about 10 times, the amount of extract liquid supplied from the bottom of the tower.
The flow of the extract in the column is disturbed by 0-, and if it is too small, the monomer degree distribution in the column tends to vary significantly.

As explained above, in the present invention, (1) Since the monomer is injected during circulation of the extract to improve the monomer concentration, even a small amount of monomer can be uniformly mixed midway through the line.

c'2I Since a liquid blowing nozzle system using an extract circulation line is adopted, the concentration of monomer in the extract in the vicinity of the sprinkling hole is uniform due to high energy (diffusion of the extract and chips inside the column). is achieved, and oligomer removal at the top of the column is extremely effective.

(3) The dispersion nozzle and the suction nozzle are located at almost the same level, which helps in the diffusion of the S-recycled liquid that is spewed out, and also allows the high-concentration monomer circulating liquid to be returned to the bottom of the tower.
This makes it possible to prevent 0- and further improve uniformity.

Example A continuous washing tower of 0.7 yrt in diameter and 9 ml in length as shown in FIG.
Caprolactam tip (diameter 2.3φ7W/m, length 2
．． sm/m) were washed continuously. The chips were supplied and the chips were discharged at a rate of t6ONy/hr, and the extract (pure water) was supplied into the column at a rate of 210 B/hr at 115°C.

Extract circulation m is 2.5 m/hr, and the amount of monomer injected is 16
The monomer content of the extract liquid overflowing from the top of the column was controlled to be 13.5%. In addition, the residence time of the dip in the column was set at 13 hours, and the high concentration upper layer (
Tower top area) is 4 hours, low concentration monomer layer (bottom area) is 9 hours.
A monomer dispersion nozzle was provided at a position such that 1-1r.

In addition, there is a conventional pure water cleaning method that does not include a dispersion nozzle (liquid circulation line 6), that is, pure water is supplied from the supply nozzle 4 at the bottom of the column, and is brought into countercurrent contact with the chips moving downward, while being brought into contact with the discharge nozzle 5 at the top of the column. Conventional equipment that discharges waste (
Conventional example), and in FIG. 1, 100% concentration monomer is supplied to the dispersion nozzle 9 via the monomer supply line 19, the communication pipe 14, etc., and liquid circulation is performed only by dispersing the monomer from this dispersion nozzle 9. A comparative example using a simple monomer injection device is shown for comparison. Table 1 summarizes the conditions and results of these examples, conventional examples, and comparative examples.

(Left below) Table 1 As is clear from Table 1, the present invention has a remarkable effect of removing oligomer components compared to conventional pure water cleaning, and also requires less injection time compared to simple monomer injection cleaning. It can be seen that the uniformity (improved cleaning effect) is very good.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory view without showing a specific example of the present invention, and FIG. 2 is an enlarged view for explaining the dispersion nozzle section of FIG. 1. 1... Tower body, 4... Supply nozzle, 5... Discharge nozzle. 6...Liquid circulation line, 9...Dispersion nozzle. 10...Suction nozzle, 18...Circulation pump. 19...Monomer supply line, 20...Engraving of bomb drawing (no change in content) 8. Figure 1. Figure 2. Procedural amendment (method) % formula % 1. Indication of case Patent application No. 1987-20769 2. Name of the invention Continuous cleaning device for poly-7 medium chips 3. Relationship with the person making the amendment Patent applicant Sashibe Okamoto, 11-11 Minamihonmachi, Higashi-ku, Osaka (300), Representative of Teijin Limited

Claims (1)

[Claims] The polyamide depths containing monomers and oligomers are moved downward from the top of the washing tower, and the extractant is moved upwards from the bottom, bringing the chips into self-flow contact with the extractant to continuously extract and remove monomers and oligomers from the polyamide depths. In polyamide chip cleaning equipment, there is a cleaning liquid dispersion nozzle located in the middle of the cleaning tower and a corresponding J for the dispersion nozzle.
A liquid circulation circuit is formed by connecting the suction nozzles and the dispersion nozzle to a pipe line having a circulation pump installed outside the column, and a monomer is quantitatively supplied to the liquid circulation circuit. A continuous cleaning device for polyamide chit I, characterized in that a supply nozzle for injection is connected.