JPS6125608A - Separating film for water-soluble organic material and separation of water-soluble organic material utilizing the membrane - Google Patents

Abstract

PURPOSE:To provide a pervaporation separating membrane for water-soluble org. materials having high permselectivity and high permeating velocity for liquid as well as high mechanical strength by using cellulose ester expressed by the specified formula as activated layer. CONSTITUTION:Cellulose ester expressed by the formula such as cellulose dodecanoate, is dissolved in a solvent such as chloroform, and the soln. is coated on a base body such as porous propylene film by casting or dipping, and the solvent is removed by drying. Using the separting membrane having an activated layer comprised of the cellulose eser obtd. by this method, water-soluble org. meterials are separated from aq. soln. of the water-soluble org. materials by the pervaporation process.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a water-soluble organic substance separation membrane and a method for separating water-soluble organic substances. More specifically, 1 the separation membrane is made into a lump and the mixed liquid is placed on one side, and the other side is evacuated to keep the absolute vapor pressure low, or the partial pressure of the target component is kept low by flowing an inert gas. A water-soluble organic substance pervaporation membrane that separates a target component from a mixed liquid by permeating the target component liquid due to the pressure difference on both sides of the membrane and evaporating it on the low pressure side, and a water-soluble organic substance pervaporation membrane using the same. Detailed methods for separating organic matter.

b. Background Art The pervaporation method is a separation method devised for the purpose of separating liquid mixtures that cannot be separated by ordinary distillation methods. Examples of such liquid mixtures include azeotropic mixtures, near-boiling point mixtures, and mixtures containing compounds that are easily denatured by heat. Such a separation method has already been described in US Pat. No. 2.953,502, for example.
Separation of azeotropes using polyvinyl alcohol-based membranes in the specification.

U.S. Pat. No. 3,726,934 discloses separation of an organic mixture using a poly7-crylonitrile membrane.

In addition to the above, other pervaporation separation membranes have been used so far, such as polyethylene/l polypropylene, cellulose acetate, polyamide, polyurethane, and polytetrafluoroethylene, but these generally have poor selective separation properties. It is bad, and the permeation rate of the tank is also low. Therefore, practical kg
In order to achieve A', if the membrane thickness is made thinner to increase the liquid permeation rate, the mechanical strength of the membrane decreases, so the device structure becomes complicated to strengthen it, and the selective separation is poor, so a multi-stage separation device is required. It had some drawbacks that had to be addressed.

Under such circumstances, the inventors of the present invention have arrived at the present invention as a result of intensive research aimed at obtaining a selectively permeable membrane with high selective separation performance and liquid permeation rate, as well as excellent mechanical strength.

DISCLOSURE OF THE INVENTION The present invention is a water-soluble organic substance separation membrane having an active layer made of a cellulose ester represented by the following formula, and a method for separating water-soluble organic substances using the membrane.

The cellulose ester according to the present invention is produced by esterifying cellulose with an aliphatic monocarboxylic acid having 7 to 21 longitudinal atoms.
The resulting omniscient polymer (e.g. C, J, Ma1
m*Ind, Eng, Chem.

(See Volume 43 # (3) + Page 684 (1951)).

Such aliphatic monocarboxylic acids include heptane l
l, octanoic acid, nonanoic acid, methyloctanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, bentadecane powder, hexadecane 1!2.
In addition to saturated fatty acids such as octadecanoic acid, hexadecenoic acid, lytic acid, oleic acid, and liluic acid.

Unsaturated fatty acids such as undecenoic acid can also be used.

The cellulose used as a raw material is available in the form of pulp or powder, but it may also be raw cellulose obtained by saponifying cellulose; i1% W acetate with an alkali. Cell 1-τ is ', s' Esterification with carboxylic acid may be any method that can obtain a sufficient degree of esterification to demonstrate the usefulness of the present invention, but the above-mentioned C0J-
The carboxylic acid pride-pyridine method of Maim et al. K. is preferred. The degree of esterification suitable for the present invention is 2.0 or more, preferably 2.5 or more. This 3-sterling degree is L
ee B, Genuag et al.
m, Ana1. Ed, vol, 13 (61p 36
9), cellulose ester was hydrolyzed with 0.25 N NaOH095-ethanol water droplets and excess ONm'OH was removed with 0.2 N klcl.
It was determined by titration.

The membrane of the present invention has practical strength and has a membrane thickness of 0.5 mm in order to obtain sufficient permeation flux. O1-500, especially 0.05-11
Preferably it is 00a.

In order to obtain a film of such thickness, a known film forming method such as extrusion molding or solution casting method is employed. cast t
As S, chloroform, tetrahydrofuran and
and toluene are preferred.

The membrane of the present invention may be in the form of a flat membrane, hollow fiber, etc.
It is also possible to combine it with a porous support. As the support for forming the pot into metal, a porous film made of polypropylene, polyethylene, polytetrafluoroethylene, or the like is preferable because of its resistance to casting agents. The pore diameter of the porous membrane is preferably 0.
5-0.01 μm, more preferably 0.2-0.0
It is preferable that it be in the range of 1 pm. When obtaining the membrane of the present invention using these porous membranes, it is sufficient to coat a solution of 1 to zovt-fl of cellulose ester dissolved in the above solvent by casting or dipping, and then dry the solvent.
・.

The membrane of the present invention is useful as a selectively permeable material for water-soluble organic liquids, and is particularly excellent in selectively permeable for aliphatic furfurs having 1 to 8 carbon atoms. explain in detail.

Reference example (synthesis example of cellulose decanoate) 16.2
JF's regenerated cellulose was charged into a reactor equipped with a stirrer and a cooler, 33.2 I of pyridine was added, and then 1 l of toluene was added.
Add 00Ii and stir the system. A mixed solution of 72.1 # of toluene and 2.1 F of dofhonic acid fluoride was added to the mixture over 15 minutes, and the mixture was kept at reflux temperature for about 24 hours. After the system is cooled, it is diluted with toluene and the cellulose decanoate is precipitated in ethanol. The thus obtained polymer was subjected to Tuxlet extraction in ethanol.
A purified polymer was obtained by removing impurities by tlK. This product showed a degree of esterification of 100- by the titration method described above. (Cellulose substitution degree: 3.00) Pervaporation experimental method The pressure on the supply side of the organic liquid mixture was atmospheric pressure, and the permeation side (collection side) was conducted under a reduced pressure of 0.3-1 unless otherwise specified. The above mixed solution was supplied to the active layer surface (ultra-thin film surface) side of the membrane, and the supplied solution was circulated while maintaining the temperature on the membrane surface at a constant temperature. The effective area of the membrane is 11. It was ocd.

The components that permeate the membrane are condensed and collected, and the amount of permeation (Flax)
(ha floor/ga・hrf) was found in the contested position. In addition, the composition ratio in the collected liquid was determined using a TCD-gas coomadogram, and a separation image a(α) of the membrane was obtained.

Incidentally, the separation coefficient a is defined by the following formula VC.

However, Xmu and XI indicate the weight percent of the ^ component and B component in the feed liquid, Ymu and Yit indicate the weight percent of the A component and B component in the collected liquid (permeation side), and A is a component that easily permeates. as an ingredient.

Example 1 Cellulose Δsdodecanoate obtained by the method described in Reference Example was dissolved in chloroform to make a 5 wt solution, applied to a polypropylene porous membrane (Di-Lagard [F] 2400, manufactured by polypropylene), and air-dried. The thickness is 37.
A composite membrane of 0 am was obtained.

When we conducted a pervaporation test on a 10vt% ethanol aqueous solution using this product, we found that the permeate concentration was 40.5wt% (α
Member: ♂: 6.81), permeation flux 1. Eye Xl0-'#・m
−”·m−+ was obtained.

Comparative Example 1 Under the same conditions as in Example 1, an ethanol pervaporation test was conducted using a cellulose≠triacetate film (film thickness 20.9 μm), and the permeate concentration was 0.4 vt% (a
f, Shio H: 0.04), permeation flux, 2.36
When I F' is #·m”·S-weight, water permeates the membrane more selectively, indicating that the cellulose trizocaate membrane of Example 1 is a membrane with excellent ethanol selective permeability. Ta.

Examples 2 to 4 In Example 1, instead of cell p-sudodecanoate,
Cellulose octanoate (degree of esterification 93.7%)
)-decanoate (degree of esterification: 99.3%) and -hexanoate (degree of esterification: 83.7%) were similarly made into a composite membrane from a chloroform solution on a polypropylene porous membrane, and their ethanol permselectivity was evaluated. evaluated. The results are shown in Table 1.

Table 1 Pervaporation performance of ethanol aqueous solution using Cellule ester membrane Examples 5 to 10 Methanol and n-purpanol were obtained using the cellulose octanoate composite membrane used in Example 1.

Impulpanol, n-butanol, a! A pervaporation test was carried out on aqueous solutions of fluorophore and inoctylfurfur. The results are shown in Table 2.

Claims (1)

[Claims] 1. The following formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [However, in the formula, R is the same or different, and is a hydrogen atom or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R
_1 represents an aliphatic saturated hydrocarbon group having 6 to 20 carbon atoms. ), and out of the three Rs in the cellulose unit skeleton, at least two are ▲There are mathematical formulas, chemical formulas, tables, etc.▼. ] A water-soluble organic substance separation membrane having an active layer made of cellulose ester made of bonding units represented by: 2. The water-soluble organic substance separation membrane according to claim 1, wherein R_1 is an aliphatic saturated hydrocarbon group having 7 to 16 carbon atoms. 3. The water-soluble organic substance separation membrane according to claim 1, wherein the proportion of hydrogen atoms in said R is 1/6 or less. 4. The water-soluble organic substance separation membrane according to any one of claims 1 to 3, wherein the active layer is supported by a porous support membrane. 5. In the method of separating water-soluble organic substances by pervaporation from an aqueous solution containing a small proportion of water-soluble organic substances, the following formulas ▲ Numerical formulas, chemical formulas, tables, etc. Or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R_
1 represents an aliphatic saturated hydrocarbon group having 6 to 20 carbon atoms), and at least two of the three Rs in the cellulose unit skeleton have ▲a mathematical formula, a chemical formula, a table, etc.▼ be. ] A method for separating water-soluble organic substances, characterized by using a water-soluble organic substance separation membrane having an active layer made of cellulose ester consisting of bonding units represented by: