JP2011099050A5 - - Google Patents

Description

The water content of the ethylene-vinyl alcohol copolymer pellets obtained from the step of obtaining the pellets is desirably less than 10 parts by weight with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer .

Regarding the saponification method, any one of a batch method, a continuous method (belt method), and a column method can be adopted depending on the target saponification degree. For reasons such as reduction of the amount of catalyst during saponification and the saponification reaction proceeding with high efficiency, it is preferable to use a tower type apparatus (not shown).

When the carboxylic acid is added, the content of carboxylic acid in the EVOH paste obtained after the main washing step is a value measured by a titration method and is usually 10 to 10,000 ppm, preferably 50 to 3000 ppm, more preferably EVOH. Preferably it is 100-2000 ppm. If the content of carboxylic acid is too small, the effect of containing carboxylic acid tends to be insufficient, and conversely if too large, it tends to be difficult to obtain a uniform film. In addition, the density | concentration of carboxylic acid in wash water is 10-3000 ppm normally, Preferably it is 20-1000 ppm, More preferably, it is 30-500 ppm.

When the carboxylate is added, the carboxylate content in the EVOH paste obtained after the main washing step is usually 10 to 5000 ppm with respect to the EVOH paste in terms of metal in atomic absorption analysis. Is 30 to 1000 ppm, more preferably 50 to 700 ppm. If the amount is too small, coloring may occur during melt molding, and if the amount is too large, the melt viscosity may increase. In addition, the density | concentration of the carboxylate salt in washing water is 10-3000 ppm normally, Preferably it is 20-1000 ppm, More preferably, it is 30-500 ppm.

When adding the boron compound, the content of the boron compound in the EVOH paste obtained after the main washing step is usually 10 to the EVOH paste in terms of boron (after ashing and analyzed by ICP emission spectrometry). It is 10000 ppm, preferably 100 to 8000 ppm, more preferably 100 to 7000 ppm. If the content of the boron compound is too small, the effect of improving the thermal stability is small, and if it is too large, gelation may occur or moldability tends to be poor. In addition, the density | concentration of the boron compound in wash water is 10-3000 ppm normally, Preferably it is 20-1000 ppm, More preferably, it is 30-500 ppm.

When the above phosphate compound is added, the content of the phosphate compound in the EVOH paste obtained after the main washing step is usually converted to phosphate radicals (analyzed by ion chromatography) with respect to the EVOH paste and converted to phosphate radicals. 1 to 1000 ppm. By adding so as to be in the above range, coloring of the molded product and generation of gels and fish eyes can be suppressed, and if the content is too small, a tendency to color during melt molding is seen, conversely If the amount is too large, gels and fish eyes of the molded product may be easily generated. In addition, the density | concentration of the phosphoric acid compound in washing water is 1-3000 ppm normally, Preferably it is 10-1000 ppm, More preferably, it is 20-500 ppm.

According to the above configuration, a paste consisting of a mixture of EVOH and water / alcohol introduced into the tower-type cleaning tank 2, with wash water in, by the feeding action and gravity by the screw, the paste inlet on the upstream side The outer surface of the paste enters the inside by the shearing action that occurs when passing between the propellers and the shelves facing each other while being smoothly transported from 2a to the paste outlet 2b on the downstream side, and Then, the paste is kneaded so that the inside of the paste comes out, and the surface layer of the paste is sequentially renewed, and sufficient contact with the washing water is performed.

According to the above configuration, a paste consisting of a mixture of EVOH and water / alcohol introduced into the tower-type cleaning tank 3, as in the first embodiment, in the wash water in, by the feeding action and gravity by the screw, The paste is smoothly transported from the upstream paste introduction port 3a to the downstream paste outlet 3b, and the shearing action that occurs when the paste passes between each rotating pin and each fixed pin, The paste is kneaded so that the outer surface enters the inside and the inside of the paste comes out, and the surface layer of the paste is sequentially renewed to make sufficient contact with the washing water. Therefore, also in the tower type washing tank 3 of the second embodiment, alcohol, impurities, etc. in the paste can be efficiently dissolved in the washing water.

<Saponification process>
A methanol solution of the above-mentioned ethylene-vinyl acetate copolymer, from which the residual vinyl acetate in the reaction solution had been removed, was fed at a rate of 30 parts by weight / hour from the top of the plate tower, and at the same time, the acetic acid in this copolymer A sodium hydroxide methanol solution of 0.54 parts by weight / hour was fed from the top of the column with respect to the number of moles of the group. On the other hand, methanol was supplied from the lower part of the tower at 60 parts by weight / hour . The tower internal temperature was 120 to 140 ° C., and the tower pressure was 0.36 MPaG. A methanol solution of EVOH was obtained 0.5 hours after the start of charging. The EVOH has an ethylene content of 29 mol% and a saponification degree of 99.5 mol%, and the paste contains sodium acetate corresponding to the sodium content of sodium hydroxide as a saponification catalyst. The “MPaG” unit is a unit in the gauge value and indicates a difference between the absolute pressure and the atmospheric pressure.

<Preliminary washing process>
Next, the methanol solution of EVOH was supplied to a tower-type washing container (10-stage tray tower). The sampled methanol solution of EVOH was continuously supplied at 80 parts by weight / hour from the top of the tower-type washing container to the second shelf. On the other hand, steam at 130 ° C. was continuously supplied from the bottom shelf at 60 parts by weight / hour , and the methanol solution of EVOH and the steam were brought into contact with each other countercurrently in the tray tower. The temperature in the tower-type cleaning container was 120 ° C., and the pressure in the container was 0.2 MPaG.

A) Washing (kneading / stirring) conditions • Screw rotation speed: 60 rpm
-Clearance between screw and tank inner wall: 10mm
-Clearance between screw and shelf: 10mm
-Tank temperature (at the water temperature before the outlet): 79 ° C
B) EVOH paste conditions ・ Supply amount: 17 parts by weight / hour ・ Supply paste temperature: 80 ° C.
・ Paste residence time: 3 hours ・ Discharge amount: 6.4 parts by weight / hour C) Wash water conditions Wash water composition (relative to water)
Acetic acid 160ppm
Sodium acetate 200ppm
Boric acid 110ppm
Sodium dihydrogen phosphate 80ppm
Calcium phosphate 150ppm
-Supply amount: 16 parts by weight / hour-Temperature: 85 ° C
The bath ratio (washing water weight / paste weight ratio) was adjusted to 0.94.

Then, from the paste outlet 2b of the tower-type washing tank 2, EVOH water / methanol paste that becomes a mochi-like cloudy high-viscosity paste: 54% by weight of EVOH resin, 45% by weight of water, 1% of methanol (100 parts by weight of EVOH) to 83 parts by weight of water, to give methanol and 2 parts by weight) acetate 1360Ppm, sodium acetate 530 ppm, 4550Ppm boric acid, sodium dihydrogen phosphate 80 ppm, the calcium phosphate 150 ppm.

Claims (8)

  A paste made of a mixture of an ethylene-vinyl alcohol copolymer and an alcohol or a mixture of an ethylene-vinyl alcohol copolymer and water / alcohol is introduced into a tower-type washing tank, and this tower-type washing tank Kneading by applying a shearing force so that the surface and the inside of the paste are repeatedly exchanged while contacting with the washing water in the inside, and discharging part or all of the alcohol together with the washing water to the outside of the tank A method for producing an ethylene-vinyl alcohol copolymer, comprising a main washing step of obtaining a water-containing ethylene-vinyl alcohol copolymer-containing composition with a low content.   The paste is introduced from the top of the tower-type washing tank and led out from the bottom, the washing water is supplied from the bottom of the tower-type washing tank and discharged from the top, and the paste and the washing water are The method for producing an ethylene-vinyl alcohol copolymer according to claim 1, wherein the counter-flow contact is made in the tower-type washing tank.   The tower-type washing tank is a multi-stage tower-type washing tank, and the paste introduced into the tower-type washing tank is repeatedly brought into contact with washing water at each stage while the surface and the inside of the paste are repeated. 3. The method for producing an ethylene-vinyl alcohol copolymer according to claim 1 or 2, wherein the paste is kneaded by applying a shearing force so as to be replaced, and the paste is sequentially transferred from the upper stage to the lower stage.   The ethylene-vinyl alcohol copolymer according to any one of claims 1 to 3, wherein the washing water contains at least one additive selected from a carboxylic acid, a carboxylate salt, a boron compound, and a phosphoric acid compound. Manufacturing method.   The water content of the ethylene-vinyl alcohol copolymer water-containing composition obtained in the main washing step is 30 to 400 parts by weight with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer. The manufacturing method of the ethylene-vinyl alcohol-type copolymer as described in any one of these.   Before performing the main cleaning step, an alcohol solution of ethylene-vinyl alcohol copolymer or a water / alcohol mixed solvent solution is introduced into a cleaning container, and brought into contact with water or water vapor in the cleaning container. 6. A pre-cleaning step for discharging a part of the mixture together with water or water vapor to the outside of the container to obtain a paste comprising a mixture of an ethylene-vinyl alcohol copolymer and water / alcohol is provided. The manufacturing method of the ethylene-vinyl alcohol-type copolymer of description.   Supplying the ethylene-vinyl alcohol copolymer water-containing composition obtained in the main washing step to an extruder, melt-kneading, then discharging and cutting to obtain ethylene-vinyl alcohol copolymer pellets The manufacturing method of the ethylene-vinyl alcohol-type copolymer as described in any one of Claims 1-6 provided with these. 8. The ethylene according to claim 7, wherein the water content of the ethylene-vinyl alcohol copolymer pellet obtained from the step of obtaining the pellet is less than 10 parts by weight with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer. -Production method of vinyl alcohol copolymer.